[arpad_m]

These threads always end the exact same way: predictably, someone with experience will try to contribute information that is not a carbon copy of the owner's manual, at which point someone else will appeal to the authority of GM engineering... end of discussion.

In general, corporate engineers have access to way more information than us outsiders, but (apart from a few exceptions) they aren't allowed to make decisions that are best for longevity or performance or user experience, because cost cutting, regulatory pressures, sales targets, quarterly results, shareholder benefit maximization etc. often override design and engineering recommendations.

Thus it's quite plausible that someone can provide germane, sound advice even without access to all the information that GM engineering does. Also, being in the know about engine design details doesn't automatically mean there cannot be others with more expertise outside the company.

BTW I have been using Amsoil Signature 10W-30 oil since the latest round of engine mods as recommended by Ted Jannetty, and never had an issue.