Oil Viscosity Poll

[sf5211]

Can you expand your thoughts on this? Not following what is supposed to be or not supposed to be happening in this instance.

Hi CS, what i was getting at is the modern engine equipped with ESS shuts itself down many times per trip. I was wondering if a different thickness would be bad for the engine being it has to be pumped to the top of the engine multiple times.

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[CarbonSteel]

Hi CS, what i was getting at is the modern engine equipped with ESS shuts itself down many times per trip. I was wondering if a different thickness would be bad for the engine being it has to be pumped to the top of the engine multiple times.

Ah, ok, I see what you are getting at. I would not think there would be any issues with that whatsoever. Mercedes has had start/stop systems for far longer than any of the American cars, their typical oil of choice is 0W-40, and their engines last quite a long time on 10K oil change intervals.

Modern engines have positive displacement oil pumps and are able to move oil quite easily even when cold. In addition, the oil takes a while to drain back down to the sump and thus all of the upper end is covered in oil so there is no danger of lack of lubrication that theoretically happens from a cold start.

 

[1quick1]

My dealer gave me some 6 quart 5w-20 oil changes. Now that I do them myself I do 5qts of 0w-20 Penzoil Platinum full synthetic and Mopar filter.

 

[Odyssey USA]

They are plenty of engines out there that use different viscosities depending on use case and to a degree the environment they are in (US versus AU for example) with the same bearing clearances in each engine. The 5.0L Ford Mustang is a perfect example of that using 5W-20, 5W-30, or 5W-50 with the same engine, just different use case--road versus track. The machining processes have vastly improved in the past 20 years through the use of CNC equipment so the machining is "cleaner" though most engines have not changes any clearances with the exception of the newest engines that are specified for xW-16 and xW-12.

With that said, I am still not understanding what SF was referring to in his post.

Correct. You also tune a vehicle in the conditions it will see. IE, a track, drag strip, or street vehicle. The variation will be minor for a given clearance. In the last 30 years, clearance tolerances has tightened up per inch of journal diameter. The other clearances, less so but it has improved due to less tolerance stack up due to, as you mentioned, less machining variation.

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