I was told long ago (few years back) cars that have the oil change light shouldn't need a oil change until the light says so. From a GM oil guy...

Not so Bil, For the all aluminum N* engine, The oil life monitor is set for 9000 miles. But the software involved varies it a bit. After my initial change out at 1000 miles, the second one was done at 9400 miles (8400 on oil) with 15% life left still showing on the oil life monitor. The third change is due with the monitor showing 9% life left at 18,000 miles. Which puts 8600 miles on the second change. I used Castrol Syntec for both changes. Use your oil monitor, its, there for reference, OnStar uses it to tell you when to change it, and your warranty covers the engine relying on it. Why waste money?

There is a Great deal of new research on the net showing Synthetic doesnt break down like Dino and that actualy leaving it beyond 5000 miles slows metal content gain in the oil, in otherwards, 5000 miles into using syunthetic,...... the oil is working better for you than when new. It doesnt seem right, but several reports accurately measuring metal content curves bear this out.

Here'* a page bearing this out with Mobil One
http://neptune.spacebears.com/cars/stories/mobil1.html

Same for Amsoil
http://neptune.spacebears.com/cars/stories/amsoil.html
Notice most gains in metals and contaminants slow as the oil ages.

For what Synthetic costs, and data available, I'll use my oil monitor and save a few bucks.

Thanks for the info Venom. I am still learning a lot about our N* motors and sure do appreciate all the help I can get.

I switched to Mobil 1 in the fall and plan to do the changes myself every six months which runs about 8k miles. When I changed it in May I think it was just over five months, so probably around 7-7,500 miles and I believe the oil monitor was still about 45%.

Venom.. sorry I didn't include ya.

99% of the vehicles here..the 4-6K rules applies as you can read it in the owners manual.

YEP, I wouldnt dream of taking an antique iron block past 3K,... but this thread was started by a member who wants info for his "GXP".

I'm running Amsoil and the amsoil filter in my Diesel truck and in my T/A

I go 25K or one year in the T/A on oil and filter, this is the normal service interval.
The Diesel I go 15K/1 year, which is the severe service interval.


Let the flame war from Bill begin.