Originally posted by warmonger:

Also, those relative weights are not really accurate. The weight of the base oil is the first number. The second number indicates the thinning resistance. Thinning being a bad property for oils and the reason they add additives. The polymers help reduce thinning. THe thinning resistance of a heavier oil is the best, but its low temp properties will kill a motor, hence the multi-weight.



This is only correct for dino juice. The base weight of synthetics are from the 2nd number, and do not have VI improvers.

More info:

http://members.rennlist.com/oil/Motor%20Oil%20101.htm

I'm using 5w-30 dino juice for the first 3000 miles on my Noble M400 (3.0L duratec, twin turbo). From my oil pressure gauge, it seems I can afford to drop pressure down just slightly. I'm going to 0w-20 Mobil 1 after the 3000 miles are up.