Add Diesel to the Engine Crankcase? Let's see what happens! 

Decades ago we ran 100% turbine fuel (kerosene) and no oil in an old inline 6 cylinder engine that was rattling like a tin full of marbles for a few minutes at idle and couldn't believe how much crap it flushed out when we drained it. We repeated this until the turbine fuel came out clean and the engine purred like a kitten for years. No damage, no metal, no loss of compression. Secret is don't rev or load the engine and don't run it for too long. You have one of the best channels on YT!! Thank you!!

What I love about this Chanel is it's pure science. Results are results.

I have worked on several engine that have had diesel in the oil. On the older cat engines like the C15 or 3406E it was actually fairly common. The o-ring would split at the top of the injector allowing fuel into the crankcase. Those engines were always really clean inside.

Yes, when I first started working as an apprentice mechanic in the early 80's, we would get cars in the shop from elderly people who would never let their engines reach operating temp that would be packed with sludge from the condensation and oil mist mixing. The condensation will form when you shut your engine down no matter what. The key is letting all the condensation burn off before you shut down the next time you drive . It was a really messy job and it would work bout 50 % of the time. Sometimes the sludge was the only thigng holding them together, because they would never change the oil or rarely. We would fill the engine to the brim and let it sit overnight in the worst cases. Pull the valve covers and sometimes the intake as well and EGR passage would be packed and why the car would quit running.. There would still be layers of sludge that would need to be knocked off even after sitting overnight. We would run the diesel fuel through coffee filters and use it to flush the engine and then flush it with clean at the end to make sure the stuff at the bottom of the pan and pickup would get pushed out, You would have to keep pusing a a screwdriver through the ol drain hole to keep the chunks flowing , Finally fill with oil and let it get hot hot, change once more and send it down the road. 50/50 chance the engine would survive, Mostly big V8's Cadillacs, Buick' Olds, Crown Vics. Mostly elderly people. Not really an issue with 4 cylinders since they heat up a lot quicker and back then old people drove big American cars with V8's. We had one Mercedes V8 that didn't survive. The Timing chains on the overhead cams would stretch out from the dirty oil/ no crankcase ventilation. and wouldn't be worth fixing.

I've started adding a half cup of diesel to my son's breakfast cereal every morning.

Back in the 70's I worked on a dairy farm. Every time they would buy a used vehicle for farm use, they would drop the oil and run diesel fuel in the crankcase for about 5-10 mins, drop it again and presto! - a sparkling clean engine. Since I was in my teens at the time, I had no idea what they were doing. But I watched it with my own eyes one day on a car that had always been run on Pennzoil. We removed the valve covers and it was caked with sludge. After the diesel flush, it was amazingly clean. Since we never ran it over idle during the flush, the extent of wear on the bearings in particular may have been minimal, but that was a time and place when anything that ran was a good thing. They even taught this in the local HS shop class.

Excellent demonstration, I have been doing that sence 1968 In the military we had a hard time getting oil filters, so I would wash the filter the best I could and flush the engine with diesel mixed in the oil, but only at an idle. Drained the oil and diesel, then pour a final quart to flush any remains left in the crank case put everything back together. and was able to go another 50 to 100 hours, with the hour meter. I kept track with the machines log. until I left the service. I still do the flush today and now the filter are easy to get. This allows me to run my vehicles for years. I have sense gone to senthetic oils which are better. However I still like to do the flush on my engine, it keeps it really clean inside. I am now over 74 years of age. I like to practice what works for me. Berrymans 12 mixed with the diesel and oil works wonders to remove gum and varnish from inside the engine with each flush. I ncver race or rev the engine this prevents thin oil problems with lubrication. Always be willing to try new tehnology but with care. As well as fore thought.

great video! I ran an Oldsmobile Custom Cruiser 420,000 mi. and flushed the engine once a year by adding a quart of diesel to the dirty oil before change. The engine was super clean at rebuild... Just let it IDLE for 10 minutes. Very effective.

I acquired a GM vehicle with a 400 small block. The previous owners had never change the oil in 75,000 miles. They just kept adding to it. The amount of sludge was indescribable. I manually removed as much sludge as I could before flushing with diesel. Fully draining the crankcase and reapplying straight diesel, I ran the engine for 15 minutes. There was no visible evidence of destruction. But the Removal of sludge and deposits was extremely evident. This was an older engine, not subject to any warrantee so risk is minimal. The engine and vehicle lived to travel the roads another 20 years to my knowledge.

You use 10W-30 as a baseline, but could you run a bearing dry in the lubricity tester to show how well a product works compared to nothing at all?

My experience with diesel in engine oil is from when my friend bought an old Honda (car). When we opened the cylinder head on the engine, the oil had dried in so much that it looked like gravel. So the choice was to completely take down the engine or try to wash / dissolve the old oil. Here's what we did: We first drained the old oil, then mixed 10w40 with 50:50 diesel and poured it in. Let the engine run until it got hot. Drained the oil. For the second round, it was 75:25 oil: diesel. Drove the engine at idle for about 5 min. Then emptied it again. For the third time we drove in pure 10w40 to wash out the diesel. Then we drained the oil and changed the oil filter and poured in new oil. Six months later and the oil was still like new

The feeling you get when you are looking for answers and find a 3yo video from PF giving it to you and you know you can trust it!

Sorry I am a bit late to the show. Love your work!! In the early 90's my Dad gifted me a 1977 Caprice Classic for my 25th birthday. He had purchased it with a 1984 Camaro 305 engine installed. The guy told him it was a "low mileage" engine. Well, it barely ran. I brought it o work and an old guy by the name of Hubie that hailed from "middle of the sticks" Missouri , told me that I had either a flat cam or stuck lifters He told me to buy 4 oil filters, 17 quarts of oil and .75 gallon of diesel. Drive the car at least 100 miles on 4 quarts of oil and 1 quart of diesel. Then change it out until you get back to straight oil. He then says, "If that don't fix the problem, bring her over and we'll tear her down and rebuild her." I didn't know what to say. The guy was the nicest old man I ever met but I didn't want to toast the engine. In the end I took the leap of faith and I am not kidding you that the car ran right as rain by the last oil change. I another 80k miles on that car before selling it to get a truck. Old Hubie never steered me wrong. If he is still alive I bet he would love your channel!!

Idk when I’m ever going to find myself in an emergency with only diesel and no oil but I still find myself watching all your videos lol. Your scientific method approach to these tests really helps me believe the results!

You put a lot of time and money into your vids you deserve a lot more views and subscribers .Thanks .

I had this happen by accident on my John Deere chore tractor one winter. It never used any oil when I checked it, it was always full and it never dripped when parked. Left it idle in the yard one day and I caught it dripping. I have no sense of smell so I couldn’t detect the diesel. Engine oil analysis showed mostly diesel in the oil and a 5% viscosity of what it was supposed to be. The company even called me and said don’t use the tractor. Rebuilt the injector pump and problem solved. Since then I do an oil analysis every change and I cut open the filter. No noticeable loss of power and it’s not making metal that I can see at oil changes. What saved me is it never ran at high rpm while feeding the cows and never more than about 10 minutes at a time. Enjoy your videos and usually learn a bit from them. Thanks for sharing your experience.

Your videos are awesome thank you for them. I watched many of them and realised with the intense things you put your engine through as a pro I as a amateur should be able to fix a engine with some tlc. I took a 1954 car that has not run in at least 30 years from my dad. Not only did you give me the courage but also a lot of trick and tips. I now have a working 1954 willys jeep. Happy thank you.

Every third oil change on my Toyota diesels, I add diesel to the crankcase and allow to idle for several minutes. The sludge that comes out when drained is astounding, and the engine runs very smooth. I’ve been doing this for just over fifteen years to the same two engine and it’s never let me down. We did it often on ship engines in the Navy prior to carrying out crankcase inspections too. Thank you for the great projects you do, I enjoy them all very much.

Who else comes here before we do our shopping list, Great to have a honest man to tell us the truth about the products. Thank You

I have been binge watching your videos for weeks; don’t know how I found ya but glad I did! No cussing, no agendas, just straight facts (often about products I will never own or use enough to be a factor).

It’s a new Gasoline-powered parts washer! :)

Back when I was a teenager when it came time to change the oil in my 6 cyl, 60 chevy, I added a quart of an off the shelf motor flush prior to the change. I noticed that it was a clear thin solvent. I also noticed that the idle speed was lower after adding the flush. This told me that the flush had lowered the overall lubrication of the oil. I was not thrilled with that observation and never added a flush to my oil prior to change or otherwise after that time. I don't think the 5 or 10 minutes idling significantly damaged the engine, I just did not want to subject it to that lower lubricant quality again. Fast forward 15 or so years and my dad experienced a diesel injection pump shaft seal failure that dumped a gallon or so of diesel fuel into the fresh rebuilt engine's crankcase along with the 8 to 10 quarts of motor oil. Most likely it ran this way for a few days or weeks before he discovered it. We both thought the worst, that surely engine damage ensued. However, that was 25 years ago and the tractor is still running fine. Of course he changed the oil upon discovery of the issue. So, I was actually surprised at how your lubricity tester showed visually more wear with the diesel fuel mixed with the oil. I enjoy these videos and tests. I would also like to see you split the case and inspect the bearings before and after these types of tests.

Old diesel engines had oil dilution systems so that you could bleed a little fuel in the crankcase in extreme cold weather. It was an accessory on engines used in places like Alaska, north Canada, etc. The engine wouild start and when it got hot the fuel in the oil would boil off. Aircraft engines had this too, such as the Rolls Royce Merlins in the P-51. But you never wanted to use too much.

I used 4 qts of kerosene to clean crank case my 1949 IH Farmall Cub tractor. I ran it until the engine RPM's started to go down only a few minutes, then drained it out and changed the oil and filter. The results were great.

By the way, thank you very much for your videos. I’ve watched several of them and they are all informative, well presented and educational. Great work!

Your test methods are great keep up the good work! And thanks for all the effort you put into your tests!

Just want to say thank you for doing all these tests. Very interesting to see how all products work. Keep up the good work and God bless

My dad showed me this trick years ago. The time/quarts in oil pan/diesel used ratio was way more than what I was taught. I used this trick on my S10 and it ran 15 before I gave it to my nephew and its still running strong. Thanks for the video I really enjoyed it.

I've watched every single video of yours. I always give a thumb! Thank you for your videos!

Man I just love your videos. Reminds me of when I was 14 and used vegetable oil for a two stroke mix. My friends all said I couldn't but my moped smelled like I was making french fries and it ran fine. Only did it for one tank but didntt see any damage when we tore the engine down.

Best content of RU-vid, sincere and enjoyable, not controversy or drama, just entertainment.

An old timer friend of mine let me use his lift when I had to do the rear main seal on my truck. Since I was having to pull the Cats off anyways, he recommended that I do a diesel flush in my crank case. This is a guy Who I trust very much. He’s level headed with a lot of expieriance. His instructions were to put 5 gallons, yes you read that right, of diesel directly into the crank case. Then start the engine and not touching the throttle at all let it idle for five minutes. Having both cats removed was imperative he told me. I followed his instructions except I added 5 quarts of oil just because I was a bit nervous. Lots of stuff came out when I drained the block down, not terrible mind as although having high miles my truck has always gotten regular oil changes. It ran perfectly fine afterwards. I have put close to 20,000 miles on since then, with no issues. I recently had to drop the oil pan and there was no signs of shavings or anything in it.

You’ve got a great channel here and it’s extremely interesting! I love it! Keep up the good work!

I absolutely have... Did a head gasket on a 3.4 Grand am... Surprise surprise lol... "Cleaned" the engine with straight diesel before the initial oil fill and start up, just to make sure it was clean. Simple cycled the engine over without the fuel pump relay a few times, and I was amazed at what came out, even after having the head cleaned and plained...

I used diesel in an old Chevy suburban to clean up my crankcase. I just cranked it and didn’t allow it to actually start and it worked very well. This was in conjunction with a head gasket repair where antifreeze was in the crankcase. Thank you for your videos! Love them!

2022 testing methods here, it's great to see how you are constantly updating the testing methods also like adding a 'splash guard' on the bearings test for example

In 1993, I swapped 4.9L straight-six engines in a 1976 F-100 I heard about putting diesel fuel in an engine crankcase if the engine has sludge built-up. So I poured: 3 quarts 30W engine oil 1-quart transmission fluid 1-quart diesel fuel New oil filter I started the engine, I’m sitting in the driver seat watching the gauges, oil pressure needle showing pressure, just listening to the engine run; after less than a minute of running, the oil pressure fell to ZERO, I turned the engine off and drained the oil pan. I installed 5 quarts of 30W motor oil and a new oil filter, started the engine, it ran normal with good oil pressure! That truck was driven for 15 more years! I have NEVER tried this again and I would not recommend anyone else does it either. Moral: The diesel fuel thins out the engine oil too much and a cam driven oil pump cannot pump it, it’s not thick enough (Viscosity too thin)

You're a cool dude. I don't say this much, but i like you.

FYI: In the aircraft I learned to fly 1932 Beechcraft D-17, It was an approved procedure for cold weather opps. to turn a valve which adds fuel to the 5gallon oil reservoir. Fuel would evaporate after a few hours of operation.

It's great that you have so many videos going back so many years. I was watching random sludge videos and the comments on those said to try putting diesel in the oil and flushing it that way. I search if anyone has tried that, and your video was the top result. The comments on this video are fascinating too. This channel has the best community.

Thanks for taking the time out of your life to make these videos bro.

After watching this video, this morning, I pulled a quart of oil out of my '95 Jeep YJ 2.5 cyl with 165K, and replaced it with a quart of diesel. I let it run 4 minutes. The engine was warm. Afterwards, I changed the oil and filter and took it for a drive. First thing I noticed, as you'd expect, the oil was very thin and poured out of the crankcase quickly. The second thing I noticed, was that the oil pressure took a solid 3 Mississippi to register and hit normal. I don't remember this happening before. I don't notice any change in the way the engine sounds or runs. It's still pretty noisy, though I think that's just the way this thing is, especially when cold. I don't think I'd do this again, as I didn't really see any benefit. I also don't think the engine was dirty to begin with, just has a noisy lifter or two when cold. I hope this feedback helps.

We saved alot of old sludged up engines back in the day by adding 1 qt of diesel with 4 qts oil. But it was very important that the engine be idling as low as possible. This really just circulated the thinner oil until it reached operating temp. The lawn mower was running way too fast which will cause damage for sure. Love your page! Please keep up the good work!!

You, sir, are someone to be looked up to and respected. This was 3 years ago and you continue to respond every single time. You might not be the BIGGEST “RU-vidr” out there, but you’d be damn to find someone with more work ethic, authenticity, consistency and commitment. I like some “manly things” but I’m not a carpenter, mechanic, land scaper, etc but I find every single video totally interesting. You’ve helped me with several purchases and will continue to do so. You’re the man, please never stop and I’ll never stop watching.

Definitely one of the better RU-vid channels! 😀👍

Revisiting this can't believe it's been 2 years already. You seem much more comfortable on camera now. I have never used diesel as a flush but have ran about half a quart of ATF and half quart of MMO mix as a cleaner for a neglected engine(2 oil changes in 5 years and 60k miles) for the last 50 or so miles before the change. I don't know if it's working or not but haven't seen any concerning amount of metal and no strange sounds. Honestly if something happened to the engine it gives me a reason to crack into it 😂. One thing I have always wanted to see is if dish soap and water misted into the intake would clean the engine.

It would be interesting to see the compression after re-running the engine with oil

This guy must become the US president. The whole earth need good guys like him ✌😁

I was watching your video "2-Stroke Oil in 4-Stroke Crankcase? Let's try it! " wondering how diesel would work as "oil" and found this video in suggestions... Man you never fail to amaze me with your ideas, keep it up, love you vids!

you do a great job on your videos keep them coming

One of the best channels on RU-vid. Extremely helpful content.

I worked on Diesel engines for a major manufacturer. When the truck engines had a little fuel in the oil, it made a huge difference in the cleanliness of the engine, with no harm. You could see a dark ring around the wear pattern on the bearings if there was fuel in the oil though.

Kerosene is pretty popular to add to the oil for cleaning the block

This going to solve some mysteries that I've pondered for many years. I've used diesel mixed with motor oil as a crankcase cleaner, but have always wondered what straight diesel would do to engines.

Kerosene’s the other one hear quite frequently. I’d be nervous to try anything but oil! Glad you’re brave enough to test these theories! Keep up the good work! You keep me out of trouble!

I appreciate all the hard work you do on these videos. Regarding the diesel in the motor to clean the motor. In an extreme case of sludge in an old Buick motor my friends father took off a valve cover and saw all this sludge built up in the head. It's was almost like a jello mold of the inner valve cover. So we all got a turn scraping the gunk. So in order to rinse out the rest. He put in 1/2 kerosene and oil. And ran the engine and drained out the oil. It was all black and lumps were plopping into the drain pan. So bright idea to put straight kerosene and go for a drive. After dumping in a gallon or so he takes it for a short drive. He got on the freeway in his trust wildcat and after along time their house phone rings and its the old man a few miles away the with a thrown rod and hole in pan. So after getting it home and him having to take the bus to work all week we pull the motor and put a junk yard motor in the next weekend. Thinking the oil pick up got fouled and spun bearings until 2 siezed and the rods came out. One was stuck in the frame in a hole it pierced. I follow your channel all the time is a favorite. Thanks

Loved the video, how about comparing diesel cleaning vs over the counter "engine flush"

I don't put anything in my oil for cleaning. I just change it regularly and keep up the maintenance. I never had a sludge issue. I have bought used cars that had seen a lot of abuse, I change the oil several times and they clean right up.

I rescued a 1966 Austin Healey BJ8 that had been parked for 28 years. It was not hard to get the engine running and I just started driving it and changing the oil every 3000 miles. Each time the oil immediately turned black. I idled it for about 5 minutes with just diesel in the crankcase. It came out black. But subsequent oil changes looked brand new until the next one. I parked the car for 5 years. Now I am bringing the car back to life using your testing as a guideline. Thanks!

Very interested in seeing lubricity test / other comparisons between several two stroke brands (like Motul, Repsol, Castrol, etc). The dirt bike and street two stroke crowd will love it!! Thank you for your awesome videos and dedication

I think that if you try the same test with ATF, you'll find that it cleans just as well without the damage. Mix about 1 to 10 with the oil and run it about 15 minutes, after it warms to running temperature, and check the filter. No extra metal! If you do that once a year (spring time is best for small engines) it will keep 'em happy for a long time. I use it for my vehicles. About half of a quart in the crankcase just before a oil change. And you can put the other half in the gas tank when it's down to a couple of gallons for the top end. Seems to do about the same as MMO but I think it's cheaper, around here anyway. Great videos. I like the way you try to keep it on a pretty much equal footing. Keep up the good work!

I love your little engine window. Pretty darn nifty man!

Congrats on 1 million subscribers! Great content keep it up 👍

wow , this question has been spinning in my head for a while!! thanks

When I was a Volkswagen dealer mechanic back in the 70's I encountered on several occasions vehicles that came in with an issue of high gasoline usage (pour mileage). in nearly every case (except for fuel injected cars) the problem was a leaking mechanical fuel pump diaphragm. Fuel would leak from the fuel pump down into the crankcase, thin out the oil, vent off from the heat into the crankcase ventilation system and then on to the carburetor causing a very rich fuel mixture and performance problems and smoking as well. These engines typically were in okay shape because the customers brought them in "in time". before any serious damage. We replaced the fuel pumps, changed the oil and adjusted the valves and sent them on their way. The interesting thing was the internals of these engines were extremely clean. Sparkling clean, all be it, with a slightly shorter life span.

Suggestion for the "grand finale" of that engine - use dish soap in the crank case. I bet it blows some good bubbles out the crankcase vent before it dies.

I love that kind of restrain laugh face on Todd every time he explain what he's gonna do in every video.

I have an old chevy 350 with about 130,000 miles. It was my grandfathers so it had sat for a long time and I found a lot of sludge in the pan. It began to tap real loud as if a lifter was stuck. I removed the pan and scraped the sludge out, installed 5 qts. of 5W-30 and a pint of diesel. When I started it, it tapped and then freed up. I ran the diesel/oil mixture for about 6 minutes, drained it filled it with fresh oil and it has never tapped again. Everytime I change the oil, I add 1 pint of off-road diesel to a cold engine, run it for about 5 - 6 minutes, drain it and fill it. This really worked for me. I also do this to my small engines but with of course a lessened diesel amount. Great video thank you.

Lawnmower: [arrives on Todd’s farm] so many new friends! Later: 😭

Best videos out there buddy! Keep it up!

I love that he refered to the transmission fluid experiment from the past

Old 6.2 diesel 230K miles. Drained oil, filled with diesel, ran 5 min cleaned out and changed oil 2 times in a week. Not sure if it made a difference but made me feel better about the abuse the engine had in the past, another 100 K so far. I was afraid of ports getting clogged, but no issues. Keep up the videos. Thanks.

Awesome stuff! This is like having our own test laboratory on RU-vid. =)

A friend had sticking lifter problems in their GM V6 engine. This was evident from a clicking sound that started after driving a few kilometers. I drained the engine oil and then added half inexpensive engine oil and half diesel fuel. After running the engine for ten minutes at idle speed, the engine was drained of the diesel-oil mixture and refilled with new inexpensive engine oil, and a new oil filter was fitted.The engine was again run at idle for another ten minutes. That engine oil was drained to remove as much as possible of the diesel-oil flushing mixture.The engine was then refilled with new quality oil and a new oil filter. The clicking sound was no longer apparent and I was told that the car ran better following this treatment. Cheers, Peter

I've never used diesel in my crankcase, BUT I'm glad l found this video and channel! Thank you!!

I just found this guy and I cant stop watching awesome videos!!!

I've been working with diesel engines for more than 20 years. You can be concerned if some of the injectors start pouring diesel in the cylinder because eventually, it will go in the crankcase and mix with the oil but it's not a disastrous event as long as you fix the problem and change the oil. Diesel fuel has some lubrication properties but I would never recommend using it to clean the engine. I wouldn't recommend any engine cleaning product anyway. The best course of action is to change the oil on time and let the engine live its life.

I Recommend this Show to every Intelligent Human i encounter. Next time show us something that you use religiously on your motor vehicles but haven't shown us yet. Keep up the Fantastic work.

Fantastic! Adding a small amount to the oil seems to be the most effective and safest option.

Good video. The last two vehicles I had where I added diesel to the crankcase, was back in the day with my '61 GMC with a small V6, and a '69 International Harvester with a V8. I only added the diesel (a quart) just before an oil change and idled it for 5-10 minutes. I never really noticed any problems in doing this and I think it removed a considerable amount of gunk. In the early 70's I discovered Marvel's Mystery Oil (MMO) and now, top this day, use it. I put the MMO into the crankcase when I am 500-1000 miles away from an oil change. With today's modern synthetic engine oils (which I use), it is probably overkill, but I still do it and do not have sludge problems with engines. Again, good video. Thanks!

Remember old diesel had a high sulfur content which added to it's lubricity. Diesel fuel after 2009 I think has no sulfur, and diesel injection components have to be built out of other stuff now.

I bought a Pontiac 455 from the junk yard 25 years ago. It was a low mileage (37k) motor out of a Bonneville. I put it in my GTO with a new cam and lifters. The inside was really sludgy. I'm assuming the car was owned by an older person who just putted around town. Upon starting it up for the first time the whole passenger side bank of lifters ticked. I had adjusted the valve lash visually when the intake manifold was off so I knew it was correct. I removed the valve covers and there was no oil coming through the push rods to oil the rocker arms on the passenger side only. I added a quart of trans fluid to the crankcase and let it idle for 15 minutes. Then I drove it around the block. No luck. I was about to give up and return the motor to the junk yard for an exchange when my brother in law suggested putting some diesel in it. I figured I didn't have anything to lose. I added a quart of diesel and then let the engine idle for 15 more minutes. Still no luck. I decided to drive the car about 5 miles up the road and then back and then pull the motor. I drove the 5 miles up and then slowed and pulled into the turn around to drive the 5 miles back. As I pulled back out and started accelerating the passenger bank started to quiet down one lifter at a time until the engine was quiet. It had cleaned itself out. When I got back home I immediately drained the very hot oil. It looked like oil out of a big rig it was so black and nasty. I put in fresh oil and a new filter on and drove the car for a couple of years with that engine. Amazingly the brand new cam survived. It must have gotten enough lubrication from the crankshaft slinging oil on it. And how did the engine run after that? Best of a 12.5 seconds at 108mph at the local drag strip (KCIR).

This is one I missed somehow. Brother I really like your videos. The are informative and very well put together. I can only imagine the bone yard of mowers and engines. Praying you and your family are safe, healthy and happy. Blessings from NW Montana.

Great video, thanks and very thorough testing.

First time seeing your videos. Love it, I'm a mechanic as well it's nice to hear someone else that actually knows what there talking about. I sunk my 4 wheeler today so was searching for ideas on what im gonna do. Thanks for the videos!

Just a side note. I would only do this on extremely dirty engines where the sludge is more of a danger than the diesel. Not on a slightly dirty engine.

I know this is an older video, but to add my personal experience- I had a jeep a couple years back, and it was horribly neglected, sludged up… I first drained the oil, left the filter with oil on it, and added diesel… probably 80% diesel mix… idled the engine for 15-20 minutes, drained it all off, new filter, and ran 50% diesel, 50% 10w30, idled for another 15-20 minutes. Finally drained it all, and went back to 100% oil and a new filter. It did a good job clearing sludge from the valve cover, and top of the head. I believe the key is to not load the engine, or rev it… that jeep is still on the road today with no knocks or any noises

i really enjoy your informative videos , i find your subject matter most interesting , as you answer alot of valid questions. keep up the great work .

When we sub marine a atv ill flush with kerosene or diesel but never run with it. This proves why,lol. thanks as always man,you do great work.

Absolutely use 1/4 diesel to oil in crankcase to clean engine. Works like a charm. Have done it on many ‘new to me’ vehicles, as you dont know the maintenance schedule followed,even if there is no signs of huge sludge build up in oil pan or in valve cover. Last one was a ‘08 G5, it had 138k km on it already, but was obviously abused. It cleaned up nicely and there is now 232k km on it. So sign of wear, runs great.

Seeing replies over 6 years later shows so much dedication. Incredible channel.

The pool pump motor repair guy approved ! that was good info farm man

would be nice to see how much boost a stock lawnmower engine could take from an IHI RHB31 Turbo ^^ Could also be a fun gokart project ;)

This was in 1976: Bought a 66 Pontiac Tempest with a 389 2bbl in it. Oil was BLACK but full on the stick, drained out 3 1/3ish quarts of hot tar, changed filter. Filled with 5 quarts of diesel, showed about 1/2" over on the stick. Idled for about 15 minutes. Idle oil pressure dropped from 30 with the tarry original oil to a little over 15 on the diesel. Drained out about 6 1/2ish quarts of mud. Changed filter again filled with 5 quarts of diesel again. Idled for 10 minutes oil press still at 15+, drained out about 6 quarts of very dirty diesel. Replaced filter again, filled with 5 quarts of Valvoline 20 wt. Idled for 10 min, oil pressure rose to about 25. Drove 25ish miles. Drained out a little over 5 quarts, kinda dirty, including filter. Replaced filter again, filled with 5 quarts of Valvoline 20w50. Engine had gained an immense amount of power over this experiment. It had multiple noisy lifters when I started the process, they had quieted down nicely by the end. Exhaust / blow-by smoke was pretty bad at the beginning, nothing visible by the end. Numerous oil leaks popped up on the valve covers and one on the rear corner of the oil pan, snugging the bolts fixed them. I used new cheapie filters with the diesel to make sure they didn't plug up, used Napa Gold for final. On the next oil change, I added a qt of Slick 50. HEY! It was supposed to work! (1976) I wouldn't have done anything so severe if the engine was in better running condition to begin with. Have had several friends copy my method with several different vehicles with mixed results. Consensus is: if it may be a basket case, not much is lost by doing this and it may find a gem in hiding. I will do the add a quart of diesel, not to exceed 25% of total oil, to a warm engine and idle for 10 minutes before changing oil if oil is dirtier than normal. Stopped the Slick50 years ago. Not very scientific, but dead reckoning tempered with experience, sneak up on doing this, you could cost yourself some serious money. There are NO miracles, only little tweaks. Good Luck! 68 yr old retired electronics geek. Michael in Colorado.

Great Video as always!! Keep them comming!!

This is one of the best channels on RU-vid.

I'm not mechanic but I'd bet the best thing is to change your oil with some cheap oil, wait a day or two after driving and then change it again with good stuff. I'd think that would help clean it without the chance of damage.

"Loss of Lubricity" sounds like a terrible Lifetime Original Movie.

@ 4:03 Thank you for investing in our product (the red lawnmower). I´m sure it will give you many more hours of trouble-free service - if not, give us a call just kidding

Thank you for all the informative video's I've wasted so much time watching and learning on. You are one of the best on utube.