FYI - GM has a listing of approved oils at:
http://www.gmtechlink.com/images/iss...ds/synthgd.pdf
Note that only 3 oils make the GM4718M approved list. Here is a blurb from a recent GM Techlink about this:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> We recently received this e-mail from Mike McQuoid, at Norman Gale Pontiac GMC, Cedar Knolls, NJ:
“In the March 2005 issue of TechLink, there is a list of motor oils approved by GM for use in gasoline engines. I'm curious why so many “full synthetic” oils are listed in the “non-synthetic” list and not in the synthetic list.”
Here’s the answer from GM Powertrain:
“GM4718M is General Motors' High Performance engine oil specification. Oils which meet GM4718M tend to be made from synthetic base stocks, so it is often referred to as a "synthetic" specification.
“However, not all oils, synthetic or otherwise, are capable of meeting the stringent requirements of GM4718M. Only the oils listed on the GM4718M Registered Products sheet have proven their performance to the specification.”
http://www.gmtechlink.com/images/iss...e.html#story18
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