Thick vs. Thin

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I was poking around Valvolines website and ran across this in the FAQ.

“Is it ok to use 5W-30 in a car if the owner's manual calls for 5W-20?

Valvoline does not recommend doing this. Using a heavier grade than recommended may cause decrease in fuel economy, higher engine loads and eventually shortened engine life. Using a lighter grade than recommended may result in excessive mechanical wear and reduced engine life. For maximum engine performance, follow the recommended motor oil viscosity and maintenance schedule provided in your vehicle's owner's manual.”

Higher engine load and leading to shorter engine life with thicker oil vs excessive mechanical failure with thinner oil. Did not really get a straight answer from Valvoline. 🤦‍♂️

I guess the age old debate will never be settled. I can picture Bob Uecker beer commercials (Taste great vs. less filling). That just made me thirsty 🍺.
 
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They're completely wrong. Most manuals say to step up to a thicker oil if racing, driving extended high speeds, towing, etc. Thinner for fuel economy, thicker for protection. Both extremes within reason of course. You wouldn't want to track your Corvette with a 0W2 (yes that's actually a real oil!!) yet you wouldn't want to use 40W70 in your Prius.
 
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Their response is all about liability. They aren't going to tell you to deviate from the OEM recommendation.

A 5w-30 will not harm anything in an engine that calls for 5w-20. Bearing heat may increase slightly, fuel economy will suffer slightly, but that's about it.
 
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I like the fact that Toyota, in the owner’s manual for my wife’s 2021 4Runner, gives us the option of running a higher viscosity than the suggested 0W-20 “if the vehicle is operated at higher speeds, or under extreme load conditions”.
14DE4263-CA80-4862-BD6D-7719D8739BF5.png
 
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KY, USA
Valvoline does not recommend doing this. Using a heavier grade than recommended may cause decrease in fuel economy, higher engine loads and eventually shortened engine life.
And now I know why my '88 Ford Escort Pony only lasted 518K miles and was only getting 40-45MPG on a regular basis. I was using 10w40 in an engine spec'd for 5w30. Oh, I forgot the the engine was still running when I retired it.
 
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That's true but "shortened engine life" is a little extreme!
Yeah, I'd like to hear their explanation on the claim that "using a heavier grade than recommended may eventually shortened engine life".

Does that mean if an engine manufacturer specifies 0W-40 then it won't shorten engine life because it was the "recommended oil"? :D
 
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Australia
For a non tracked vehicle the thinnest allowable viscosity would be the best. ;)
Unless your doing 140mph extended hot laps, then I'd strongly recommend using the highest allowable viscosity.
 
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I like the fact that Toyota, in the owner’s manual for my wife’s 2021 4Runner, gives us the option of running a higher viscosity than the suggested 0W-20 “if the vehicle is operated at higher speeds, or under extreme load conditions”. View attachment 44294
👍👍

Plus, there's the overseas manual that shows up to 20w-50 in the T4R.

Got 5w-30 in mine right now and will be going with 5w-40 later. (All changes with UOA which will be posted...eventually)
 
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FL, USA
Proof right there that thin oil is for economy and thick oil is for protection.

Too thick and oil WILL cause issues, too thin an oil WILL cause issues. There is a middle ground. You can have an oil that will provide better fuel economy and better wear resistance upon cold start / short trips (thinner). You can also choose a thicker oil that will provide better wear protection during high load / high speed conditions. Lets be honest though, most of us are doing short trip driving to the grocery store and around town where thinner oils shine.
 
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Dallas,Tx USA
Too thick and oil WILL cause issues, too thin an oil WILL cause issues. There is a middle ground. You can have an oil that will provide better fuel economy and better wear resistance upon cold start / short trips (thinner). You can also choose a thicker oil that will provide better wear protection during high load / high speed conditions. Lets be honest though, most of us are doing short trip driving to the grocery store and around town where thinner oils shine.
Yes absolutely!! That's why I feel there's always the perfect equilibrium. W30's are thin as necessary and also thick as you need (W30's were in fact a fuel economy oil at one time, yet they're also popular in the muscle car crowd). I'd never use a 20W50 in my Accord.
 
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