Engine Oil Codes Explained, SAE (Society of Automotive Engineers) numbers - Oil Viscosity Explained 

BEFORE COMMENTING - Gets thicker when hotter? Really? Please can I just ask before any more comments regarding this question come in, that you please look at this video that I made explaining further what I meant when I said this. This explains in much more detail and hopefully will satisfy your desire to know more. Here it is. Thank you. Craig: : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Tck6JU-KZgQ.html

The fact that oil is engineered to be LESS Viscous when colder is incredible. Thank goodness for whoever came up with that

The simplest explanation on viscosity I have ever received

As an engineer i state these about oils: The second number (the working number) is the most important as that defines it's viscosity near working temperature. This relates to the oil pressure and bearing clearances.. better clearances may use a thinner oil as it is not spewed right out of the bearing. If bearing journals are worn and inherently the oil pressure goes low you might want to go for a higher second number to grab a bit more life before total rebuild. It will be thicker at work temperature and will have increased pressure than the thinner oil.. but because of the wear.. the pressure will be about the same with the thicker oil. The problem is not solved fully because different parts wear different.. so while boosting pressure for crank journals, valve guides may be starved of oil because it's too thick, or turbo bearing that is still in parameters needs a thin oil.. so the thicker oil for a worn engine does not solve issues and it may create more issues if you skip too many numbers. The first number represent mostly the viscosity dependency with temperature. The lower W number, the more stable viscosity with temperature the oil has. So lets assume a monograde SAE30 oil (for agriculture tractors etc).. it has a set cP viscosity chart depending of temperature. That chart is quite steep.. very viscous at low temperature and adequate for running at 100deg. Hypothetically there is a monograde oil SAE5 that has the same steep curve of dependacy but it has reasonable viscosity at low temperatures and way to thin at 100deg (as thin that it gets a 5 rating compared to 30-40 usually for engines). The 5W30 is the multigrade oil that performa at cool as the monograde 5w and at hot as the monograde 30. So in any case, for engine oil.. a 0W30 might be the best you can buy and most recommended.. because its viscosity gradient with temperature is very flat.. almost constant.. same viscosity at cold or hot.. the higher the first number is, the less flat that curve is and more depended with temperature until you reach the monograde SAE30. The points of concern for using a very thin oil at cold .. so lets say your manufactures say to put 10W40.. you definitely can opt for 0W40.. better, more stable viscosity with temperature, no harm done, same viscosity at running temperature. The caveats for this are the price (is way more expensive 0W40 than 10W40), and the shortcuts and bad additives added that may be just for flattening the viscosity with temperature but having all kind of side-effects worsening other characteristics.. so putting 0W40 when is not needed may not be economical and from some aspects may not perform better. The best thing to do for an engine: check the manual (and find the manufacturer recommends from 5W40 to 15W40 in hot areas and from 0w30 to 10w30 in cold areas).. living in a hot area you put the best 5w40 it was recommended. Check the manual further and see it recommends to comply with BMW LL-01 oils standard. Check carefully on the label and your oil should state a list of car manufacturer standards.. make sure your needed standard is on that label!!! this is a set of key parameter an oil has to meet in order to pass the standard (so it may state to have certain additive, certain concentration of different stuffs, etc) - this is the most important thing! Another quite loose criteria could by API rating.. S for spark (gasoline engines), and C for compression (diesel engines). The second letter is ranging from A to N depending of it's quality and better properties.. the higher the letter, the better properties of lubing it has (better friction reduction, better onctuosity, better flash point, better..etc). Now SA is from the 20's i guess.. so you get today SM, SN, or CF, CI (diesel engines are heavily loaded.. and only qualifies for a lower letter standard). Another thing VERY important in choosing the right oil: If the engine oil is used in more the one place, take great care to satisfy all recommended instructions (viscosity rating SAE, and manufacturer standard, also the API and ACEA ratings to be fulfilled), because some engines use the engine oil for actuating variable valve lift and timing, and in such applications, viscosity and other properties must be the same because the hydraulic distributors were designed with a certain oil in mind to work.. make sure you put the right one. Also in motorcycles, most of them use the engine oil for the wet clutch.. so you don't want to slip.. so usually in motorcycles it's a compromise.. a worse enough oil so the clutch wont slip.. a good enough oil to prevent wear of the engine.. in reality is neither of those.. and recommend an SJ api rating (very old rating.. a bad enough oil that still lubes something). I could write books about oils.. but wait... I already did.

I can't tell you how much I appreciate the time you spent on your explanation here! I've asked countless car accessory store staff about this over the years and not one of them knew the answer. I'm off to show my kids this so they know for future reference. You are a legend!

Watched at least 10 videos on the subject and your is by far the best (and pretty much the shortest). Good entry-level explanation - thank you.

Great video, can't understand why people would thumbs down someone for educating them!

Awesome, finally an excellent way to explain for me an non-mechanic! Thank you for sharing your thoughts and wisdom with us!

It would be better if background music was turned off

I’m studying to become a archipelago Captain here in Sweden. And we have a test coming up in our machine class. This helped me alot. Thank you very much. You just earned yourself a sub! ⚓️

Thanks man. People like you make life easier and worth living.

I have a repair shop and my mechanics were having a really hard time in understanding oil configuration numbers. This video solved our problems, very well explained! Thank you very much for sharing it.

Sir you changed my world!!! 😐 I was always confused buying my oil for bike. after trying several times, as I usually learn the hard way, I sticked to 10-40. it suits me well and give me great acceleration and top speed. many many thanks and respect from Pakistan!😘😘😘

As a mechanical engineer it help me a lot. Thank you🙏🙏🙏

Great video. One thing you did not mention is the temperature that the cold or "W" part of the oil is tested at. Unlike the second number that is tested at 100 degrees C, the cold number (W number) is generally tested at -35 or -40 degrees C. In other words, VERY cold temperatures. Far colder than most will encounter. With that said it is important to remember that while both numbers on a multi-grade oil such as 0W-40 are tested to SAE standards, they are tested at very different temperatures meaning they are not exactly on the same scale. Using the 0W-40 as an example, one may think that as the engine heats up to 100 degrees C, the oil actually thickens as you are going from a 0W to a 40. This is not the case as the two grade numbers cannot be directly compared as they were created using different baseline temperatures. Therefore, the oil is actually getting thinner as the car warms up to 100 degrees C and reaches its 40 rating. This can be likened to comparing Celsius and Fahrenheit. Just because 60 degrees Fahrenheit is a higher number than 20 degrees Celsius does not mean it is warmer. In this case, 20 degrees Celsius is warmer than 60 degrees Fahrenheit, despite the representing number being lower.

All these years and I never understood this. This video simplifies it.

Thank you so much! been reading endless none-sense on the internet and your video made it very clear and easy to understand! Simple is best!

This video finally demystifies everything about engine oil. Thanks for sharing!

Lovely simple straightforward explanation. A great job mate well done

5w-50 thanks to the great personality who cleared all the doubts about oils 😀

Awesome explanation. You're an engineer with good teaching skills.

Good video well explained, Best with most vehicles is stay with the manufacturer,s recommendations normally found on the oil filler cap and use a high quality oil, your engine,s lifespan depends on it!!!!

Best oil vid on youtube simple and easy to understand.

wow .. after ruining though so MANY of others explanations of how to explain the oil code properly.. YOUR video explains it the MOST Simplistically and properly..THANKS !

I'm so glad that you shared your knowledge. Thank you for sharing

hi Craig, im a subscriber for your channel, a retired auto tech that still practice the field with more than 45 yrs experience in automotive, industrial and comercial machinery - industrial mech and parts fabricator any way, the way the fabricators and engineers explained the sae formulas in automechanic schools were very similar to what you just said with one slight exception: the first digits, i.e. 5W tell you the size of the molecule structure size of that particular formula for instance, if 10W way oil is not available for certain machinery using that grade or application, then you can use 5W way oil, but you cannot use 10W way were 5W oil is used for two main reasons: 1. 10W is twice as big as 5W 2. because 10W way uses a bigger molecular structure it cannot run freely into the oil galleries, gaps and critical spaces inside the machine Ωfuthermore, if a machine has been designed to use certain grade of oil, then that grade will be used always until it dies out 💀👀 today some auto parts stores' attendants ask their customers for their car's mileage and it usually is more than 100 k and they reccomend them a higher formula which is very wrong - these guys are not auto mechanics to start with it, they are just store attendants with very little automotive experience, and when they provide some kind of tecnical advice is because they have learned that on the internet, a cooworker, automotive magazines, literature that accompaign automotive parts or they have been in some seminar or auto expo but no hands on experience 👌 §if some one ask me & wants to augment the size for their application i will reccomend to add a few onces of a good quality engine oil additive but that's it; the engine formula must be respected in order to perform close to specs as possible - thanks for your time and your videos 😁👍

I found this the best one explaining about engine oil grades yet. You cleared my concept. But please use a dedicated mic for clear voice. Thank you!

Thanks very clear, best part, no distracting music blasting out.

Thank you so much for making this video. Im 39 and ive always thought 5 was the hot viscosity and 30 when cold. It just made sense so i never questioned it. But now that you explained it it actually made no sense to have an oil thin out at higher temps but actually get thicker. Pretty cool how they can make it act that way. Very helpfull video👍

The lawnmower diagram was heartfelt, Thank you sir.

Thanks for clear and understandable information, and thanks for getting right to the point!

The clearest explanation I have found on RU-vid. Thanks

Downloaded the video. Very useful explanation of SAE purposes code. Thank you for sharing!!!

i watched a lot of videos explaining the same thins but yours is the clearest one .. big thank u to u :)

The test performed at 100C uses a smaller diameter hole than the test cold. 5W-30 is NOT thinner at colder temperatures than at hotter temps, but it IS thinner than standard SAE 30 at cold temperatures. So many people get these figures wrong because they assume the two testings are equal. When testing oils at cold temperatures if you were to use the same sized hole, the viscosity would measure much higher. Single viscosity oils have a linear slope to their density/viscosity as temperature rises. Multigrade oils have a curved slope, changing viscosity sooner at a lower temperature. The first number is lower simply because the orifice used is larger.

Again, simply explained and not full of jargon....thanks

It's important to understand that the SAE number (30 or 5w) IS A STANDARD, NOT A MEASUREMENT. The car makers talk to the SAE people and come up with a number that corresponds to a safe range of viscosity for the kind of engines they want to sell. Oil companies put the SAE numbers on the bottle and are protected from lawsuits by the fact that any car that specifies that SAE number must be compatible with that kind of oil otherwise it's the manufacturer's fault, not the oil. On the other hand car companies are protected because if an oil company has a bad batch, ruins cars and the oil tests to be outside of that range, everyone knows it's the oil's fault, not the engine. So the SAE numbers only loosely correspond to viscosity; an SAE20 oil will not necessarily be half as thick as an SAE40 oil. The fact that the number corresponds roughly to viscosity is just so that the standard makes some sense when you read it (although it still continues to confuse EVERYONE). For one, motor oil does NOT become thinner as it cools. It always becomes thicker. The increase in thickness is just not as much for oils with a low w-number. If we're allowed to play the same game as the SAE, then let's at least come up with a way to interpret these numbers intuitively that doesn't lead people to the wrong conclusions. It makes intuitive sense to see the w-number as how much the viscosity increases at cold temperatures. So a 10w-30 oil would be 30 when hot, but 30+10 or 40 when cold. 5w-20 would be 25 when cold. 20w-50 would be 70 when cold. 0w-40 would still be 40 when cold. This is not strictly correct but it's conceptually adequate to explain how the numbers relate to the viscosity of the oil. As for cold starts, my experience is that it's the quality of the oil, not the viscosity that determines cold start behavior. I have had a car start fine with 15w-30 in the winter. Put in a 15w-30 from a different company, and then you would have problems. In other cases I found it was because my starter was going out, or my battery was going out, and it had nothing to do with the oil. I live in a hot climate, so 15w in the winter is not a problem except for certain brands. Car oil pumps are constant displacement pumps, which means they will pump a constant flow of oil, even if that oil has the consistency of a slushie. The problem is not that the oil gets too thick to be pumped. It's that solid oil does not flow into the gap left when the pickup tube sucks up the slug of oil it's sitting in. Then it just sucks up air.

mate thank you very much for grate explanation, i have put in my car 5w40 but dealer recommended 5w30 i was worry but after saw your video now know much more, thank you

Excellent explanations, thankyou for sharing. 👋 🇦🇺

Im running 20/70 in my old '77 hi ace lol its seems to love it ,still pulls a full load while burning a little oil ! Cheers.

So an easer way to see it 5w-30 it is 5 viscous when cold and 30 vicious when warm I think?

This video is the most logical explanation I'm searching for.

I watch this every night before i go to sleep

Every time I Watch your videos I end up understanding something I thought I knew.

best explanation , love the ac"cent ,thank you,.cheers

This is the only video you need to watch on this topic .

Nice video. I have a question. I always wondered if the 5 and the 30 are on the same scale? It is just difficult to digest that when it is always easier to change the oil on a warmer engine as it flows better. So 5 and 30 are on the same scale? or each temperature has its own scale?

Чудесна работа, сега вече зная какво е W5 ---- Great job, now i know what it is W5 Thank you so much.

thanks

I had no idea. Actually, I always thought it was the other way around. Thank you for enlightening me!

I’ve been driving for 30 years and I’ve never put the recommended oil for my car, I just pick up the cheapest one I can find and put it in and I’ve never had a problem...

Wow! 😊 Brilliant! The most comprehensive, yet concise video explaination of engine oil viscosity that I have watched. Much Obliged 😊

good well put together vid many thanks

Great explanation, always follow the manufacturer oil specification for your engine 👍

Just in case you were wondering, SAE: Society of Automotive Engineers Standard.

Super simple and straightforward explanation. Thanks!!

dont race or rev your engine in the first 3 to 5 minutes.let it run slow untill it gets warm

That now make sense to me. As I own a couple of Retro Motors and rather than shaft the engine. I now have a understanding of the oil I use in them...

well yes infact the "w" does stand for winter. sae 30 oil has a viscosity of 30 hot or cold. "seasonal equipment" also includes snow blowers and I'm confident they also take sae30. very good video by the way. I hope eventually people will realize that engineers are working really hard to get the right oil weight when designing their vehicle. but all that information is in the owner manual, which nobody reads

i think the explanation is so simple and straight forward, well done sir.

Glad I was buzzin when I watched this. You lost me at "I just wanna give a quick explanation".....🤤

I enjoyed the video. It was very informative and saved me a lot of time looking at this text book. The 5 min breakdown was really helpful. thank you. appreciated every second

So, what you're saying is that the engine oil gets thicker when its cold?

Best video ever ... He made it so easy to understand .. thankyou so much sir

the way I understand it, from owning old oil burners dating back to the 70,s that a 20w 50 oil, because its heavier in viscosity therefore when it gets hot it wont thin out as much as a lighter weight oil, therefore it wont burn off as quickly as a lighter weight oil so good for older engines that the oil rings are shot ,and the motor is on the way out ,or in need of a rebuild , but not suitable for modern cars, which some of them require fully synthetic light weight oils to even start .

Thank you very much for this valuable info. May God bless you n everyone u love.👍🏻

very well explained, so easy to understand

This is such a great vid mate! Really simple and easy to understand. Love the drawings and it’s explained perfectly 👍

This is such a clear explanation. thank you so much for sharing.

The best explanation I’ve ever heard. Thank you for sharing this sir. Regards from Perth WA.

quick question, almost all new Japanese cars run on 0w-20 these days as they are trying to push fuel economy and shorten warm up times etc. The manufacturers say they use 0w-20 so the cars have 0 warm up time. I find this hard to believe because regardless of how thin the oil is, surely it still needs a few moments to circulate and coat all the parts properly. Is it really possible to have no additional wear by using a very thin oil?

Excellent explanation for the use of the various oils. Years ago if one used Castrol GTX 20W/50 it was considered to be the best.

Actually, multi-viscosity oils are low viscosity oils with chemical polymers added to make a thin oil act like a thicker oil. Think of the polymers as chemical ball bearings. The higher the big number, the more polymers are added. Hence, on a 10W-40 oil, you're actually using a 10W oil that acts like a 40 weight oil when it warms up. This is good with a 4 stroke engine. But with a Detroit Diesel 2 stroke engine (the old 53, 71, 92, 149 and Locomotive EMD 567, 647, 710 Series), 2 stroke Diesels do not relax-they are firing every time. Hence, the polymers are always being squished down and never given a chance to relax back to their chemical size. With a 2 stroke Diesel, the polymers squish down and then you have an engine running on straight 10W. This is why 2 stroke Diesels are required to run on straight SAE30, 40 or 50 weight. Hope this helps.

I do have a question for clarification. I was a mechanic for 5 years. When I would do a simple service of a morning when the customer had just been driving the vehicle, the oil being very hot would come out of the sump very very quickly (When the numbers specify that the oil is meant to be thicker). Servicing a vehicle at the end of the day however, when it has sat in the carpark and cooled down to ambient temperature, the oil would come out a lot slower (which according to this video, it has a lower viscosity reading therefore is thinner). How does "cold, thin" oil come out slower and "hot, thick" oil come out quicker? Great video!

Thanks for posting

The best explanation ever. If this guy was my teacher I would had my master degree by the time I would be in my early 20s

thanks a lot for sharing your knowledge, it is very helpful indeed. stay blessed

One day on a trip I had to add a litre of oil to a warm engine at a fuel station. They had stored the oil outside, and ambient temp was -40 degC. I was shocked how long it took to pour the oil out of the can into the engine, about 5 minutes. Truly, molasses.

I am so confused! How does oil get thicker when its warmed up to 100 degrees??

This is one of the most useful engine oil grad video, many thanks!

what oil would u recommend for my racing mower

Really great video... VERY well explained! Thanks so much.

I tried to tell people that W on the 5w means winter. No one believes me even in college.

Simply put, the lower the w number, the less the oil’s physical properties would change due to temperature. More stable in viscosity throughout the temperature range.

But is 5W SAE 5 at both -30c and 10c? Is the transition from thin to thick linear?

Engineering Explained would have taken about 30 mins to explain this. fast and to the point i like it

Thank you for sharing, I was worried about which engine oil to use for my bike.

My oil is always cool.

I likes and respect all of modern science and technology. Kind regards.

First off, these are not codes, they represent a specific weight. Codes are what modern cars produce indicating what's called "a trouble code"

The 5 weight oil separates from the 30 weight oil into different layers, heavier oil laying closest to oil pump suction tube and is picked up first, in a cold engine. That’s why is important to let the engine warm up for a couple of minutes before reving up and driving away. Think about this, if it’s in single digits outside and you start the engine, why force it to reach full operating temperature of 100C in a matter of a few seconds like most drivers do? Just start the car and let it warm up to where the temperature gauge begins to rise is sufficient.

I always got it right but after this video I am confused... thanks to some of the people commence that cleared it up

Great explanation! I hope you are a professor or motivate some to explain that way!! Thanks a lot for saving us time!

I love this!!! I have never had engine oil specifications so simply explained.

BEST EXPLANATION I HAVE HEARD. NOW I UNDERSTAND.

That's raining on wet .. but still one of the nicest explanation ever.

Thank you for the time taken to make this very informative video. Very straight forward and easy to understand.

Excellent breakdown! Thank you.

I learned a lot about Engine Oil today thank you for teaching me something brand new that I never even knew before thanks bud

I've used SAE 30 natural oil for years and the engine is still fine!