0w40, 5w50 - are they really better?

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I still have doubts about the super wide range oils like the ones that seem to be popular in Europe. I guess their oil analysis results have been good, but how do these oils perform in a high rpm engine that is driven hard? I just don't see how they could perform as well due to the increased use of VII. Am I just stuck with the old school way of thinking. Are these oils really just as good or better in terms of being shear stable?
 

JHZR2

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I think the engines in europe are smaller and thus are driven harder then most people drive around here in order to get the speeds they drive at. I agree, youd think the oils would shear out quickly. I guess with a properly selected blend of oils with different VIs, they can minimize the VII additions. Plus, as time goes by, the oils undergo other odd processes which cause then to thicken up again. JMH
 
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YES they DO shear. I think they reason they are using them is to maintain cold cranking and economy but get a little thicker film. Instead of 5w50, I would use 10w40. Instead of 0w40, I would use 10w30. Nearly same film thickness(depending on formulation). Less nasties.
 
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No they DO NOT shear AS much as paople think (they REAL synthtics anyways) and a 5w-40 doesnt shear anymore than a 10w-30, in the long run. Most good real syn oils that are a 0w-40 or 5w-40 will shear some, but will thicken back up to a 40 viscosity oil (like M1 0w-40). However, some DO shear a bit (as much as one grade) like Shell's Rotella T syn. even so, this takes more than a few hundred miles and the shear usually stays on the upper end of a 30 viscosity anyway. Now, if the oil sheared down to a 20 viscosity oil, then id be REALLY concerned w/ it and would defintely never use a Xw-40 oil again. BUt this not the case. youre safe as can be to use them and they will not 'clog' your engine or anything either IF they ever do shear.
 

harrydog

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But in what applications have we seen test results for? Were they from the typical family sedan? I'm concerned in the stability of these oils in a high performance application. Has anyone tested them under those circumstances? They DO have greater amounts of VII's, don't they? Have VII's improved so much that they are no longer an issue at all?
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Originally posted by MikeW: Don't be so sure. Check the VOAs and UOAs for M1 0w40. There's very little difference in viscosity from 0 miles to 10K miles.
quote:
Originally posted by Jason Troxell: YES they DO shear. I think they reason they are using them is to maintain cold cranking and economy but get a little thicker film. Instead of 5w50, I would use 10w40. Instead of 0w40, I would use 10w30. Nearly same film thickness(depending on formulation). Less nasties.

 
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Again, I wouldn't be so sure that these oil use VII. They may have gotten good enough at building synthetic base stocks that they don't need VII to get wide range multigrades. I asked Redline specifically about their new 5w40, and they specificially said they didn't use VII. I seem to remember reading that ExMob didn't use any for the M1 0w40 (However his is an unconfirmed sighting. I don't think ExMob is in the habit of letting us rabble know what's in their magic potions). Since conventional multigrades start with the thin w-weight oils and build them up to the high temp weight with VII, I would expect them to shear down with age, heat, and/or stress. The fact that the M1 held up for 10K suggests (but does not prove), that it doesn't use VII.
quote:
Originally posted by harrydog: But in what applications have we seen test results for? Were they from the typical family sedan? I'm concerned in the stability of these oils in a high performance application. Has anyone tested them under those circumstances? They DO have greater amounts of VII's, don't they? Have VII's improved so much that they are no longer an issue at all?
 
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Don't be so sure. Check the VOAs and UOAs for M1 0w40. There's very little difference in viscosity from 0 miles to 10K miles.
quote:
Originally posted by Jason Troxell: YES they DO shear. I think they reason they are using them is to maintain cold cranking and economy but get a little thicker film. Instead of 5w50, I would use 10w40. Instead of 0w40, I would use 10w30. Nearly same film thickness(depending on formulation). Less nasties.
 
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