Will Thinner Oils Damage Your Engine? 

*Clarification!* There still seems to be confusion about the viscosity decreasing with heat, yet the number is higher, for example 5W-30. 1. This is explained from about 1:05 to 3:05. 2. All motor oils (basically) will decrease in viscosity as they heat up (become thinner). 3. Motor oils will increase (become thicker) in viscosity as they cool (as demonstrated in the video with graduated cylinders). 4. A 0W oil has a lower viscosity than a 10W oil when it is cold (the number is lower). 5. A 40 grade oil is thicker than a 30 grade oil when it is hot. 6. A 10W-30 (as shown at 2:28) will be thicker at cold temperatures, but thinner at high temperatures, versus a 0W-40. 7. The rating is temperature dependent! There is a cold rating, and a hot rating, which comes from tests (shown at 3:17). 8. Even though the number increases as it gets hot (like 5W-30), the viscosity decreases. It means the oil behaves like a 5 grade oil when cold, but a 30 grade oil when hot. How? 9. Viscosity modifiers are molecules that expand as they heat up, which decreases how much thinner the oil gets as it heats up. It still gets thinner, but not as thin as it could get if the viscosity modifiers were not in there. This is what makes it a multi-grade oil. Because it behaves like different oil grades depending on temperature. 10. In summary, a 5W-30 will decrease in viscosity as it is heated, however its hot rating is a thicker grade oil than its cold rating. See plots in video (2:28) to see what this looks like.

As a Chemist, I can confirm that honey does have a higher viscosity than water.

He's right, nobody with a Corvette cares about fuel efficiency.

As with any car manufacturer there is always one exception to the owner's manual. The current Subaru engines all use the 0w20 oils. The same engine built in Japan all use the 5w30 oils. There are a great many cases of oil consumption in these engines in the US using the 0w20 oils. Most when moving to the 5w30 oils can eliminate the oil consumption issues. Since I live in an area that can have colder winters I elected to run 0w30 oils in my Subarus.

I had my subaru tuned by the leading engineer of mitsubishi's efi setup, when mitsubishi closed down here in adelaide/south australia, he started his own tuning business - steve knight racetech. He told me to go higher on the second number to 50 or even 60 (so 10w50) when I do track days or go drag racing, as the oil takes longer to be displaced in the bearings and will prevent spun bearings, and never go to a smaller number unless I wanted to spin a bearing. He built and rebuilt many race engines in his life. I follow that rule, and have never damaged an engine.

"As long as the engine lasts for the warranty period, we don't care what you put in it." -Ford Executive

I'm an aircraft mechanic and I used to work in gas turbine engines.(jet engines) The synthetic oil used in those engines that reach 60 000 rpm was so thin you couldn't tell the difference between the oil and the jet fuel.

I was always told by a good family member who was a mechanic it’s thinner oil in the winter so the engine warms up faster and a heavy oil in the summer because the engine gains more heat and so far I’ve been doing it past 35 years I don’t have a problem

You can usually drop the cold number with no issues. Cars from 20-30+ years ago may call for 5-30 or 10-30 because there was no 0-30 available at that time and the dealers dealers would have to stock a new oil. I run 0-30 in older cars and trucks at our landscaping company and in my personal cars we had no oil related failures. A 0 weight oil may even provide better protection since it can quickly get into all areas of a cold motor.

"Use what the manufacturer recommends" ...until they recommend a lower viscosity on the same motor later in production to increase fuel efficiency at the expense of wear.

Use manufacture recommended oil. Mazda RX8 has left the chat.

“Always always always” as I drive back from Oreillys with 0w-40 for the winter. Great video

I love you because you said 'criterion' for singular rather than the plural version "criteria." BRAVO!

I just hope that going with lower viscosity oil to increase efficiency by 1%, is not causing 10% shorter engine life. I'd like to see data that proves that engine life isn't sacrificed at all.

"Always use what's recommended in your owner's manual." Me, channeling my inner Derek while buying a gallon of Rotella 15w-40 and a bottle of Lucas for my F-350: "It's got dinosaurs and vitamins in it. Plus, it was on sale."

Good video. Other things to consider: Over time engines have been designed with tighter bearing clearances, thus the thinner oil is needed. On the other hand, ring seal will suffer if the oil is too thin resulting in loss of power. under load.

My 2018 Volvo came with a manual recommendation of 5w-30. They actually sent me a letter with a sticker to put in my manual to change to 0w-20. I'm at 277k miles and still running strong after switching about halfway through

That's the best looking, cut away motor, I've ever seen!

I’m glad to see you are gaining industry respect. I don’t think GM shares their very expensive demonstrator models and research data with just Any RU-vidr. You have earned this kind of recognition and I anticipate it’s going to continue.

Excellent video, this what I was looking for, no one really unstood the details and explained it the way it is explained in this video

Thanks for the video. The EPA is ruining the ICE. For example, take my 2.0T Honda Accord. 0W-20 is the spec for North American vehicles. However, other parts of the world call for 5W-30. Additionally, fuel dilution is a major issue with Direct Injection engines, like mine. The thinner the oil, the more damage fuel do to the oil. These long intervals are a nightmare for long term internal damage to a motor because of that. I'll be running 5W-30 on 5,000 mile OCIs from now on, on all of my Honda engines.

When the automotive industry talks about 'adequate protection' for the 'life' of the engine what they really mean is that it won't fall apart or start smoking during a cars typical life span. That does not automatically mean a different oil won't offer more protection or extend the life of the engine. I'm skeptical of claims the automotive industry make. Automatic transmissions that are 'superior' to manuals for example where they are horribly programmed and refuse to dowshift yet upshift at every opportunity because drivability was tossed out the window in favor of fuel economy.

Surprised he didn’t mention how some car manufacturers will have a graph in the owners manual telling you what viscosity to use depending on your average or ambient temperature where you live

i used to work in an auto parts store back in the 70s...we had a 3rd option back then which was straight SAE 30.....some vehicles used it but oils got better over the yrs thus protecting more at the lower/start up temps AND the tighter tolerances that occurred as the engines got higher revving and more fuel efficient

Very interesting! I better be careful with using modern oils in some of my older vehicles, although as stated a slightly lower winter or higher summer number isn't as bad as going the opposite way. Thanks for the info.

Just subscribed and I'll tell you why. Instructions were clear and concise without overbearing music to contend with, really no "extras" thrown in just to hear your head rattle, and finally camera work was well done without shaking or wondering. This should be a lesson for other RU-vidrs. Thank You, JD

Thing with the manufacturer recommended oil weights is that they’re universal for climate regions. They’re meant for the dead of a Canadian winter or August in Texas so you CAN fudge those numbers depending on the climate where you live, just don’t go down (ie 5w30 to 5w20). Up though, especially for the year-round “hot” climates like Texas there is absolutely no problem raising those numbers. In fact it’s probably recommended. You’ll never have the low flow cold start problems to worry about but rush hour traffic on the freeway when it’s 105*F ambient and 130*F+ on the road with your AC cranking and no airflow through the cooling system your engine will appreciate the extra viscosity.

Mazda recommends 0W-20 for my engine. For the same engine, in Italy Mazda recommends 5W-30. Why? I suspect 5W-30 is a better oil for this engine and there are no CAFE requirements in Europe.

As a sales person in a parts store, I can tell you it's very frustrating and cringeworthy when someone comes in and wants 20-50 for their everyday driven 4 cylinder Honda/Toyota, etc. This happens often. I always recommend sticking to what's marked on the oil cap.

Wow, I’m a 67 year old guy who just learned some thing new! My 19 Camry uses 0 W 16 and I was wondering how could this oil protect my motor. Thank you.👍🏻

Great analysis. I would have liked to have seen some analysis for race/endurance engines on recommended race oil as I have a new C8 and I plan to enter some endurance race events where the engine will be operating at or near max RPM for 45 minutes to an hour. I have used 20-50 race oil in the past in other races in other cars.

The graph and explanation at 11:00 is fantastic. That is the most helpful thing in the video for me, and it makes complete sense.

That cut-away engine is a work of art. I would have that in my living room as a sculpture (if my wife would let me...).

Climate plays a major role in oil selection. If you live in Chicago, extremely cold starts are normal in winter. A lower "W" number can save your engine, and allow for faster warm up. But, if you live in Los Angeles, winter freezing are not an issue. During sustained driving on long freeways, and highways, and especially long trips through desert conditions, means your high end viscosity can become critical. It is always smart to allow warm ups before driving after long cold nights. Change your oil before it begins to break down. This keeps internal dirt, tar, and debris to a minimum. Always use better brand filters!

I actually remember the days of factory carburated vehicles and running a thinner oil in the winter. Good stuff and brings back positive memories.

Oil lubricates the engine Dodge 5.7 camshafts and lifters left the chat.

I had a big argument last week about this Most people want thick oil But they dont understand that thick oil cant previde lubrication when cold and thin oil can go between those tiny gaps that modern cars have now. Just use the oil the what the manufacture recommand

I had a 1964 mercury with a 351 windsor engine, I used a 10w30 oil with a can of STP It ran really good with regular tune up and oil change every 12,ooo miles

Best video in describing viscosity and the relationship with weather and engine temperature.

Loved the water skiing analogy as it relates to the piston to cylinder wall interface.....very clever !!

That demo with the grad cylinders was great. Thank you.

So clear, easy to understand for an ordinary person who is not well conversant with automobile engineering principles .. thanks dear for a wonderful guide

What did not mentioned in your video is mixing 50/50. Combining 2 quarts of 20w 50 and 2 quarts of 0W 20 on 1998 Honda Accord.

(Oil Guy forums implode) What was that noise?!? Oh, someone said “Viscosity” on the Internet.

“ALWAYS use manufacturer specified oil viscosity” Everyone in the comments- “Nah...”

I never realized the bearing drop test bud. That’s awesome 👏🏾

I’ve been trying to figure this out for years. Finally I understand, thank you!

Its funny how most people are so quick to take the advice of a friend who heard from a mechanic that doing _____ will give your car more power/reliability/efficiency. But refuse to believe what is written in the official service manual from the people who designed the thing!

The last few minutes explained it all simply for me to understand. Thanks.

Thanks .for that like always you take a very complicated subject and bring it down to a level where we can understand. That was very clear. Thank you.

I've seen technicians at dealership using 0w-20 oil for cars that are supposed to use 0w-30 in tropical weather. I looked up the manual and it specifies that 0w-20 is supposed to be used on cold weather and winters and not for summer / tropical weather. So always lookup in the owner's manual. The oil gets thinner when the operating temp gets higher. If you drive your car hard then please select the heaviest weight oil specified in your owner's manual.

Long story short: as long as the oil is thick enough to provide oil pressure that's high enough to make sure there's no metal to metal contact, it's thick enough. Any thicker is wasted energy at best and accelerated wear at worse since the excessively thick oil can't flow well enough.

I use a 0w instead of the recommended 5w on my car, but I live in Canada 🇨🇦. So the 0w is definitely better in -30 celsius.

Look his smile he enjoys informing people awsome man

Thank so much for making such clear sense of oil viscosity! It’s crazy to think I’ve been wrenching on cars for almost 30 years and I’m just now understanding what the numbers actually mean. The main reason I wanted to know is because I just had my first complimentary oil change done on my 2022 Hyundai Elantra N. The dealership put in 0W-20 when the manual calls for 0W-30. After calling a different Hyundai dealership and Hyundai Customer Care, they all confirmed despite what my owners manual says, they can put in either 0W-20, 0W-30 or 5W-40. Needless to say I was both confused and concerned. I had a Hyundai tech on one of my FB groups insisting that’s not true and I should only be using 0W-30 like the manual says. Long story short I now understand the difference between the oils and will be draining the 0W-20 and filling it back up with 0W-30 ASAP.

Best explanation I ever had!! Thank you !!

This is why I like my engine, the manufacturer specifies thicker oil for extremely hot climates, thinner oil for very cold, and one in the middle for moderate climates which is most places on the planet.

Let’s talk about oil filter bypassing as viscosity goes up.

Nice lecture, question though, what if im modifying engine like lets say increasing the compression ratio by replacing pistons, does the lowering the lower value and increasing the higher value become a must or should i still stick to the manufacturer's recommendation?

Great video, you have shown us all crucial things except one. In case that is necessary to replace prescribed oil, which number is better to match? Exemple: If the recommended oil is 20w40, and I have to replace it with a similar one, is it better to take 10w40 or 20w50 if the engine is air-cooled and it works at the high temperatures? Thanks in advance!

"You should always, always, always" Me: Haha. Lucas oil treatment goes glug.

Wife's 2016 Odyssey calls for a 0w-20 oil and was consuming a good bit after 120k miles. I swapped to 5w-30 and it runs much better and didn't notice any decrease in MPG.

Outstanding presentation. I have a much better understanding. You are very clear and precise.

Very informative and well done, thanks!

Some old motorcycle engines had components that were exposed and never saw any oil at all... Such as the tappets on the exposed valves of a 1930s Douglas. The metal was so glass hard that it didn't wear. Also most two stroke engines are lubricated with petrol that has just 1/50 th part of oil in it.

You truly are the best! Deep knowledge explained in vocabularies that are easy to understand. Captivating presentation too! Really appreciate your sharing of information!

synthetic vs non-synthetic , that's also a changing point in these oil numbers, stick with the specified grade that the car is designed for 👍👍

Absolutely superb. Quite possibly the best explanation of how important the correct grade of oil is that I have ever seen. Looking forward to watching more.

Over 35 years ago, I was studying electrical engineering in Kingston UK. We were lucky enough to have two lecturers with a boundless depth of subject knowledge and were equipped with the means to communicate that knowledge. I said at the time that as students we were enjoying a charmed education. Your presentation and communication skills mirror those days. Fantastic! Oh! And one more thing, thanks. Mike. RIP Tom S.

I've found that using thinner oils results in moderate oil consumption. When I use 5W30 my 4 cyl car uses no oil between 5000 miles OCI. Using 5W20 the same engine is about 1/2 qt low by 5000 miles. The engine has 45,000 miles.

My 2018 camry has a unique oil pump system , so ow -16 ( manufacturers recommended) is definitely my go to.

part of the issue of changing viscosity is also the oil pumps flow rate and pressure relief valve. if you use a thinner oil then you could end up with low oil pressure at low revs. if you use thicker the pressure relief valve will bypass and reduce the flow around the engine.

Did your homework man, glad to see someone telling the right things

3:31..Q Jet baby! Easily the coolest sounding secondary howl ever!

Used Mobil Oil in industrial oilfield engines since the 1960s, great performance, worth every cent.

Loved this video. Did MOBILE ONE mention that the price of gas has gone down and the cost of oil has almost doubled in the last year.

Glad to see you've come this far. Great content still. I'm basically falling asleep at night to it because of my curiosity and I'm enjoying the education, regardless of me already working on my own car

Thanks for the last 5 mins of this video. it answered many questions!

The reason these debates exist is that suddenly all manufacturers in the US magically changed to 20 weight oils overnight. The arguments that this is about bearing clearances and tighter engineering is complete garbage. Yes a 2023 car is better built than one from 1970, but not that much different from 2015. Case in point. I've owned two Audi Q5s, both B9s, both with the EA888G3 engine, a 2018 and a 2019. Under the hood and owners manual recommendation for oil for the 2018 was 5W-30 or 5W-40, and the manual indicated the decision should be made on operating ambient temperatures. In addition, there were the recommendations for formulations for the DI engine. Now in the 2019, with the identical engine and drivetrain, the recommendation is for 0W-20!!! Never ran it. Audi did this for one reason - US regulations. Both cars had a Unitronic tune for >300 hp out of the 2.0L, last thing to do is thin out the oil. Same thing with most of the RU-vid debates on this, owners see that the US owners manual recommends 0W-20, while the same engine sold in the EU or Japan recommends 5W-30. I'l

very cool engine cutaway!!

"how cool is that engine" man, that finish they put on the steel is so enticing. I wish i could touch it.

As a bear, I can confirm that honey is delicious.

Dear you have explained so well in a very lucid manner , all doubts solved

Hi, Thanks for the detailed explanation! however, if the oem from Europe reccomends 0 W20 but we are located in the semi tropical weather country, should we use 5W30? As the temperature here seldom goes below 5c . Thank you!

Back in the day when I was a Ford tech, Ford training classes always stressed that 90% of engine wear happens at cold start. So they want an oil that will come up to pressure quickly when started.

Cool video ! Had an Audi Q5 3.2 v6 gas, took 0w-40, above average mpg for that much v6, ~ 23-24mpg. Now got '19 VW Tiguan AWD, takes 0W-20 and again I average way more than the stated mpg, 30+mpg. Awesome, I'll take it :D

You should clarify that many world market engines specify a broad range of both cold and hot viscosities based up temperature and use (not just track).

Engineering Explained is great for snow storm days. I can’t put this guy away.

On my current car Audi recommend 5W30, but on a couple of occasions i found it too thin for the summer in the traffic jams to the point where the "low oil pressure" lamp came up so i drove it to the garage and after they disassembled the entire engine found out there was actually nothing wrong with it, it was just the oil wasn't viscous enough at these high temperatures (usually anything above 40°C). And because there wasn't 5W40, went for the 0W40, the problem went away immediately and later in the year i found it helps for much smoother starts in the cold winter mornings and nights. It's strange however that manufacturers don't include table with different climates and recommendation of oil grade. I remember in my 1990 VW Corrado manual the 15W40 was recommended but in temperatures lower than -15°C or altitudes above 1500m the 5W40 was noted as well as when there's a lot of short city driving.

been running 0w-40 in all my vehicles for 18 years, never gad an internal engine issue. also i live in the northern midwest with cold snowy winters.

Good description. I use a 0 w 50 in a special build where. I have . Also sheer temperatures are near 300F for mobile 1 , as well as sheer strength. Where others measure viscosity , not mention flim strengths.

I have a 2003 Ford F250 Super Duty truck with a 5.4 motor gasoline engine. I do not use the recommended oil for my truck. I noticed if I use the recommended oil 5W-30 the motor starts to make a ticking noise. It has 366,000 miles now. I been using regular castrol gtx 20/50 for 5 years now and changing the motor oil every 2500-3000 miles. I haven tried the synthetic 20/50 motor oil and my trucks engine makes a ticking noise with that one too. I am surprised how great it sounds just with the regular 20/50 castrol gtx oil. This truck does not want to give up yet. Amazing truck!

Whenever I see you I run catching my notebook . So much details so much learning. Thanks a lot.

Thank you for doing all the footwork, EE. I have often wondered about these lubrication questions.

Thanks for the awesome video. I still have something I didn't understand. Given the first number in 5w30 explains the viscosity when the oil is cold. Why is 5w40 much ticker than 5w30 when cold ? I tested it myself in a way similar to your. Aren't they supposed to have the same viscosity?

Dear Jimbo, I love watching you do ‘stoopid stuff’!

I went from 0W20 to 5W30 into VW 1,5 TSi engine with 2 cylinders deactivation. Our local weather is from -20 to +40 degree Celsius, and I believe 5W30 is the sweet spot. Car manufacturers are pressured by the EU to push the emission down so they put the low viscosity motor oils int their engines.

Always well explained, thank you!

Thank you! This was very educational

Sir you are brilliant, love to hear you talk.