No 10W-40 in Vettes?

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34,063
Location
Southern NJ
My friend who recently bought a new C5 said it says in the manual not to use a 40wt. oil yet the same car in Australia can use it. We all no why we use 30wts. in NA, but why would his manual tell him not to use it? Damage?
 

CJH

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489
Location
Pennsylvania
quote:
Originally posted by buster: My friend who recently bought a new C5 said it says in the manual not to use a 40wt. oil yet the same car in Australia can use it. We all no why we use 30wts. in NA, but why would his manual tell him not to use it? Damage?
C.A.F.E.
 
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3,023
Location
USA-Michigan
All GM cars say to not use 20W-50 and 10W-40 oils. But it says you can use them if in a foreign county if the preferred weights are N/A, 5W-30 or 10W-30. It probably is CAFE, the auto manf's are required to advise their customers to use these oils. Also I believe there are viscosity additives in some 10W-40 oils that make them undesirable for their engines, ring material incompatibility over extended miles. I read that somewhere in some GM literature but darn if I recall.
 
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USA
Conventional 10W40 are full of viscosity improvers and have been banned by most all manufactures. Synthetic 10W40 is another beast all together. Olree the Oil Czar at GM is convinced that most engine failures occur due to to much viscosity. Never mind the low oil pressure's accepted as normal. THe books on how to build a small block for raceing that have been put out by the GM Race Shop recomend 20W50 in the engines and also encorage you to replace the spring and shim it for more oil pressure before bypass. The key to remember is that they have to assume that the owner is as dense as a box of rocks and useing the cheapest Tech. 2000 oil that he can find when they make these types of generralizations. They can not account for the occasional enthusist that is going to fill the crankcase up with 10W40 Redline Synthetic. The manufactures have also gone to bed with EPA in reguards to C.A.F.E.!
 
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Greece
[QUOTE]Originally posted by JohnBrowning: [QB] Conventional 10W40 are full of viscosity improvers and have been banned by most all manufactures. If a company like Mercedes approves the use of 10W40 and use it as first oil fill in their engines i assume that there is no problem with this viscosity any more web page
 
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2,480
Yannis, that page is for M-B auto's and most, if not all 40's there are not only synthetic, but meet additional M-B specs...here we're talking about vettes... I personally think the "don't use 10-40" is a fabrication. GM has an oil spec for vettes...isn't it 4718 or something. Do any conventinal oils meet this? Anyone know more about it??
 
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8,937
Location
SC
quote:
Originally posted by Dr. T: GM has an oil spec for vettes...isn't it 4718 or something. Do any conventinal oils meet this? Anyone know more about it??
There are no conventional oils that meet the GM4718M spec for Vettes.
 

Patman

Staff member
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21,990
Location
Oakville, Ontario
quote:
Originally posted by G-Man II:
quote:
Originally posted by Dr. T: GM has an oil spec for vettes...isn't it 4718 or something. Do any conventinal oils meet this? Anyone know more about it??
There are no conventional oils that meet the GM4718M spec for Vettes.

I think it would be impossible for a conventional oil to meet this spec, not because of technical reasons, but simply because in order to qualify for that spec it must be labelled as a fully synthetic oil. I believe it also needs to be 5w30 too.
 
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