Higher Viscosity? Add less Oil??

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Oct 22, 2003
By Detroit
I don't think that works, except that the higher viscosity oil should result is lower consumption. So if with 5w30 you were using 1/2 quart in 3000 miles and, for example lets say, the 5w40 used no oil in 3000 miles, then you could put 1/2 less in to start with and end up in the same spot. But in the real world, both these grades will need some topping up.

Is it that you don't want to have the remaining 1/2 quart laying around for several months?
Yeah, there's no correlation between viscosity and capacity.

Capacity is based on engine size and engineers' calculations of lubrication needs.

Viscosity should be based on ambient temperature only (with the variant of synthetics being able to perceivably and theoretically undertake a higher load/temp. than conv).
If you run it 1/2 qrt low, your 5w-40 would run hotter and flow like a 5w-30.

Originally posted by Grossomotto:
Hey, that's why I put the disclaimer "Maybe a dumb question".

But interesting, nonetheless. I'd say you were just thinking outside the box, which is a place where there are no dumb questions.
I have a question. Maybe a dumb question. Let's say your auto calls for 5.5QTS of 5W30 and you want to run 5W40. Would it make sense to add just 5QTS of 5W40? Meaning, you would have less of the 5W40 oil in your engine than the 5W30.
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