Importance of staying in grade

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Southern NJ
Why is it bad for wear rates if an oil thins out of grade to a 20wt when this is what many new cars/trucks are calling for? Does thinning down a grade increase wear values?
 

buster

Thread starter
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34,035
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Southern NJ
I forgot about that "useless" sludge molecules that linger around. But what are the negatives of thickening other then fuel economy?
 
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3,327
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Bolivia
From what I've seen in 100's of analisis for different customers, oil that thins out has more bearing wear IF the vehicle is used under heavy loads. In light use I don't see a difference. [ May 11, 2003, 04:00 PM: Message edited by: widman ]
 
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450
Location
Louisville, KY
quote:
Originally posted by buster: I forgot about that "useless" sludge molecules that linger around. But what are the negatives of thickening other then fuel economy?
thickening mean the lube stock or some addditives have oxidized. Therefore wont lube as well. a 13cST weight thats an original 13 cSt weight is a much better lube than 13cSt that started as a 10Cst. Or for that matter, better than a 13 that started at 13 dropped to 11 and then went back to 13. Fred... [Smile]
 

Patman

Staff member
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21,989
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Oakville, Ontario
Part of the problem is that when an oil thins out like that, this means the VII is breaking down, so there are "useless sludge molecules" running around in your oil. I'd rather have a 5w20 oil that starts out at 9cst and finishes up at 9 cst than to have a 5w30 oil that starts out at 10.5 and ends up at 9.
 
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