How To Choose The Right Viscosity Motor Oil - A Certified Lubrication Specialist Explains

Working in a large fleet operation, 200 units, cars, SUVs, trucks from class 3 to class 8, I observed 1st hand the effects of 0- 5, 5-20 Each vehicle that the manufacturer recommends super light weight oils had knocks, rattles, changing to 10-30 stopped it all. Our fleet was made up of GM, Dodge, Ford, gas, and diesel engine cars and trucks in Colorado. Managing a fleet you get see the effects even before the manufacturer does.

After 50 years of doing it myself, I finally seriously researched motor oil. I came to the shocking realization that I could have used nothing but 10W-30 in every vehicle I have ever owned from the early 70s till today. In several of them, the recommended viscosity was 5W-30. However, in the fine print it always said you could use 10W-30 if the temperature never went below 0 Fahrenheit. So there.

I have a 2018 Camry V6 (the current generation) and I live in a mostly hot climate all year round. The dealer recommended me to use 5w30 and if I wanted to go for 10w40 (which they used on my car when I didn’t know better lol) there wouldn’t be a problem. Toyota engines can accept wider range of oil viscosity. I was shocked when I found out that US spec Toyota models use 0w20 oil. I have been using 5w30 full synthetic and for years and no problems whatsoever. 0w20 is too thin for that engine in my opinion.

Thanks for the great video. One thing to keep in mind, fuel dilution changes the viscosity requirement for pedestrian gas cars too. We can choose an oil that provides adequate MOFT under 100% of normal operating situations, but when driving around town, fuel can accumulate in the oil. Follow this up by a blast down the road at high speed, some towing, or a track day without enough time to evaporate the fuel, and bearing failure can be the result. The Audi supercharged V6 is well known for this.

I use what my car manufacturer recommends in the winter and put in a slightly thicker oil in the summer. Most of all, I pay attention to the night time temps. I want the thinner oil in there for cold nights. When it never gets below freezing at night, only then will I put in my summer oil. You want the oil flowing freely at start up...always.

For the new wrx's, Subaru recommends 5W-30 in the Canadian owner's manual and 0w 20 in the US owner's manual. It has to do with EPA requirements in the usa.

We need to figure out an oil and filter package for our sprint car motors over the off season. Love your content. ❤

Love your work mr Speed Jr . As you chaps say” awsum “. Together with all these other boffins you introduce , this is just the best fun. Thank you to Stapleton 42 for helping me finds you guys. Keep it gannin lads✌

Excellent video! I’ve never seen a chart that gives you a baseline for where to start with bearing clearances. I want to build a road race 454 LS7, and now I can have an intelligent talk with my engine builder. I’d like to run 0W-40 on the road course at an oil temperature greater than 212°F and still have adequate oil pressure at 7000 RPM. Hopefully going with the gas-ported, gapless 1mm, 1mm, 2mm ring package! Thanks for educating the track rats and gearheads out there!

Great video. Interesting how important the 40c viscosity is. In many climates it’s the viscosity change of the oil from say 10c or 20c to 100c that is so relevant.

Another great class! Thanks guys!

Always enjoy you videos guys!. Thanks again.

I switched my '16 Corolla to 5w30 from 0w20 at 200K miles. Now, I don't have to add a quart to quart and a half every 5K miles, my car is quieter, and the efficiency is the same for me. Owner's manuals in other countries list MULTIPLE grades for the exact same engines. This "0w20 only" nonsense is only a sop to the EPA/Feds, and I love that people refuse to accept this as per their programming.

Good video. One has to remember that with miles come wear, the clearances will get bigger thus less resistance for the oil. With higher milage you will have too use a thicker oil.

I have been using synthetic oil only in race engines for near 30 years. Road race or dirt oval engines. Have normally used 25/50. Chev road race engine did aprox 2200 race miles and the bearings were basically brand new. Good enough to reuse. Unfortunatly the crank was cracked! I did use 15/40 also, seemed no different. This on a drysumped SBC road race engine with a decent oil cooler running to 7500. Oil temp usually around 220-230degF Current project is a 5 litre Ford to 340ci. Will be run to 7500 also. The windsor oil pump drive is too small@ 5/16,, weak and I am stuck with a [good] wet sump. I feel 10/40 may be the go. Crank will be aprox 2 thou right along.

Thin oil is ok for winter months, but 5w-30 or 40 makes more sense in warm weather. Has stronger film on bearings and lowers blow-by.

One additional point, when using piston squirters, distributor gear squirters or in engines that have other forms or devices or wear that can result in oil pressure/flow escapes, (leaking timing chain tensioners or slightly worn oil pump are a good example on an older engine) The use of ultra low viscosity oil can result in zero flow to distant components. It's not that the parts need more viscosity, it's that the system as designed or operated can't provide adequate flow, often during very low RPM conditions. This is why we sometimes see the farthest cam bearing cap wiped-out first. And why a move to a more viscous oil is a viable solution.

Thanks for the insights!

Wow, I wasn't expecting to see an Oldsmobile head in this video

Many years ago I ran two different oils to test on a very hobby level, but there was almost 40 degrees *C oil temperature difference, one was Semi-Synthetic maybe 15-40 or 10-40, the other was Full Synthetic maybe 5-30. It is a long time ago, but I was impressed at the difference, it was also two different brands, so many changes. But one of them was around 95*C and the other around 135*C at full warm somewhat "hard driving" on the street, not on track. What oil was best for the motor I would guess the one that kept the heat the lowest. As long as the pistons also were cooler, and not just the oil.. Hmm.. I guess above 100*C would be nice for some water evaporation though. But what actually made me comment here, was the Cylinder head, just a random Olds head on the table.