A couple questions

[gtmay]

Being a new owner of a 1997 Grand Prix GTP, I was wondering if everyone would recommend synthetic oil. If so, what is the best oil to put in the car. My other question is how do you know when to change the SC oil. I just purchased the car 2 weeks ago and was thinking about changing the oil now just to be safe. Thanks for all the great info here on the forum.

[BNaylor]

What is the mileage on the car? I would be careful converting to synthetic in an older car with mileage. You could get leaking seals. For synthetic most of us use Mobil 1.

On the SC oil I would do that annually. All GM recommends is checking the level every 30K miles. I would change the SC oil out just to be safe. There is an inspection plug at the snout where you can drain the SC oil. Use GM supercharger oil only. See link below.

Click here

[gtmay]

The car has 110,000miles on it. If you don't recommend switching to synthetic, what would be the best choice?

[BNaylor]

Originally Posted by gtmay

The car has 110,000miles on it. If you don't recommend switching to synthetic, what would be the best choice?

If you decide to switch make sure your seals are good to include the valve cover gaskets. But I would carefully consider that decision.

There are alot of good Dyno oils and it is more of personal preference than any one product being better than another. For Dyno oil I prefer Castrol GTX. I use Mobil1 syn in my GTP but I made the switch when it had under 50K miles.

Just do the oil/filter change every 3K miles and you should be OK. Good luck.

[Scrapper]

i use rotella made by shell..even the truckers use it...and i use it in my bike...

[eippermx]

I agree with bnaylor's advice. I watched a guy put Mobile 1 in his 120K mile V-8 and watched that expensive oil drip out the rear seal, back of the manifold, and front timing cover. Funny part was to see that same engine not leak when he changed back to his normal brand. I use Mobile 1 in my '04. I changed to synthetic on that motor at 28K. My '99 has 135K and I've been changing it every 3-4K miles with Penzoil. When I transplant the 35K mile S/C 3.8 I just bought for my GTP project car, I will start it on Mobile 1. Everyone has their favorite brand of oil that works for 'em. I think the jury is still out on synthetic blends.

mark

black 2dr '99 GP GTP
Red 2dr '99 GP GT
White 4 dr '04 GP GT1

[richtazz]

I agree that switching to synthetic on a high mileage engine is asking for leaks. Synthetics actually flow thinner than their dino counterparts, which explains the leaks developing. The problem with synthetic blends is many are only 10% synthetic, yet carry a price tag halfway between dino oil and full synthetic. I would say you're not getting your money's worth. You'd be better off buying a few quarts of dino, and a few quarts of full synthetic and make your own synthetic blend. Beware also of no-name synthetics. Many are just dino oil with chemically modified molecules, but since those molecules don't occur in nature, they can technically call them synthetic. Stick with Mobil 1 or Valvoline full synthetic if you want a true synthetic.

[69goatfarmer]

I'm buying an '04 GTP with 63,000 and want to run synthetic. Is there any way to tell if what is in there now is synthetic? I"m buying off a car lot and not from an individual so I have no history on the vehicle.