My new theory on engine tolerance design and oil specs

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The problem I have with the 5w-20 debate is this: Who cares how great the UOA's for this grade are? If it doesn't protect the engine as well as a thicker oil, why use it? Heck, a straight 5 weight would have excellent shear stability, I'm sure, but who would run that in their car? Maybe 5w-20 is more shear stable than 5w-30, and maybe I could get 1 or 2 more miles out of a tank of gas. But I'm interested in my engine holding up more than I am the oil. After all, isn't it alot easier to change motor oil than it is to change the motor itself? I just refuse to believe that the engine in my car, which now calls for 5w-20, can be protected as well as basically the same engine three years ago when it called for 5w-30. Not to mention the fact that every other Ford engine requires the same viscosity oil. Perhaps the 5w-20 is a more "advanced" oil, but the fact Ford made the one-size-fits-all switch in 2001 to 5w-20 has convinced me it was for fuel economy first & foremost, with engine protection ranking somewhere on down the line. Unfortunately, I guess we won't know for some time how good (or bad) this thinner oil is for engine protection. At least not until someone has a car with well over 100K+ miles on it that's had a steady diet of nothing but 5w-20. JMO
 
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BTW, I would like to clarify I'm not trying to imply UOA's aren't important and don't give credible, useful information - so please, no attacks on that front. I simply meant I would like to see some long term, tangible evidence of how 5w-20 protects before conclusions are drawn about its' benefits. [Smile]
 

Patman

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quote:
Originally posted by cwilli01SS: Patman- You just said a few posts before you'd run redline 5w20 in your Firebird? Did I read that wrong?
That was my opinion a long time ago (you'll notice how long ago it was when I posted that) but after seeing how much my engine likes an oil that is a thick 30wt much better than the thin 30wts, I can't possibly see how my wear numbers would be any good with 5w20. I didn't have as much UOA data on my engine back then as I do now.
 
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quote:
Originally posted by MikeL: For a resonse to what someone said about thinner oils putting less stress on oil pumps freeing up more power. A few racers i knew used to do that, they claimed that running 0w-30 in there cars as opposed to 15-50 would yeild a gain of about 2-4% of power. Although i should also mention that they rebuilt the bottom end of there motors every other season.
Thats an excellent point, I also know a couple drag racers that use light synthetic oils, another trick is leaving out several qts of oil for less crank windage (such as 7 qts in a 10qt sump). In regard to the 5-20, I would agree that the manufacturers are after fuel economy more so than long term engine life, after all its only their concern for the waranty period.
 
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For a resonse to what someone said about thinner oils putting less stress on oil pumps freeing up more power. A few racers i knew used to do that, they claimed that running 0w-30 in there cars as opposed to 15-50 would yeild a gain of about 2-4% of power. Although i should also mention that they rebuilt the bottom end of there motors every other season.
 
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Good points JohnBrowning, especially #5. To go with a 5w20 because the 5w30 is going to sheer back to a 20 anyway is to give in--to admit defeat! I bet 10w30 is just about as sheer stable as 5w20 and surely it has a much better high stress sheer number. [ December 02, 2003, 12:51 AM: Message edited by: TallPaul ]
 
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