5w20 vs 5w30

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0w-30 ILSAC rarely got specified, that's pretty much why. Mobil will back 0w-30 in a 5w-30 application, and GM will allow 0w-30 in 5w-30 applications, at least in extreme cold conditions like up here (and have said that for years). So, there are limited circumstances and options.
 
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So for the whole purpose of this thread... which is truly a better route to go?

Use a quality synthetic oil of the weight recommended in your owner's manual for your driving conditions. There is no proof that doing otherwise will improve performance or longevity.
 
One of the things to consider is the amount of VII's that are used to formulate and oil. This can be guessed at by the overall spread between W eight and op temp weight. The larger the amount of VII's, the less actual oil is in the formula...

Taking this into account, the 5W-20 would be more shear stable and since it's being used mostly where it's cold, we likely have less heat spikes to break it down thermally
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So although I don't need it, I'll vote 5W-20 as the likely better of the two
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In my environment, a 15W-30 would be more appropriate.
 
Originally Posted By: AuthorEditor
Quote:
So for the whole purpose of this thread... which is truly a better route to go?

Use a quality synthetic oil of the weight recommended in your owner's manual for your driving conditions. There is no proof that doing otherwise will improve performance or longevity.

A quality oil, synthetic is not necessary in every instance.
 
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