It had synthetic from the factory, change anytime
One of the questions is which weight the other warranty. What is the factory fill weight. Assuming that it is a 5W30 I would go with the Series 3000 5W30 in lieu of the 0W or the 10W. Of the three weights the 10W is the least probable to go extended drains (beyond 7500 miles) as the 5W and 0W have a better overall base oil and additive package. However, I use the 10W in 4 out of 5 cars I own with one being a twin turbo that I change out at one year or 5000 whichever comes first. On one I go 12,000 miles.
Your MAIN issue is not oil or weight but warranty. None of the Amsoil "SYNTHETIC" oils are API certified only the XL series are so if you have any warranty issues to be concerned with do not use Amsoil until the warranty is over, stay with Mobil 1. Do not rely on the Amsoil warranty as a reason to use the product. If your new Vette requires the API doughnut and if you are concenred that a warranty will not be honored due to a non API certified oil do not use Amsoil. You would eventually win but not drive that Vette for years waiting for the court to decide.
If any issue your only real choice is Mobil 1
[ February 21, 2003, 08:04 AM: Message edited by: Spector ]