View Full Version : Oil Question?????

07-26-06, 09:41 PM
Ok. I bought my 94 Caddy SLS in april with 113,000 miles and changed the oil at the 114,000 mark. I used Castrol 10W30 high mileage oil. I've had alot of experience with Castrol from having it in a car that was driven over 500,000 miles(Castrol 20W50) and in our John Deere Diesel farm tractors. I also run the 20W50 in a 88 Cadillac 4.5 Deville that seems to be responding well to it. Over 180,000 miles on it.

Here's the question, I want to switch to a synthetic blend of Mobil Oil. What would be the best weight for a N* with 119,000 miles. I fear running heavy oil in the N*, because I just don't trust it like the older motors I've ran 20W50 in.

What do you all recommend?

Elmer Fudd
07-26-06, 09:54 PM
When in doubt, go by what the manual says. Mine (99) says 10w30. There is no note that says to switch to something else over 100k. There IS a note that specifically says not to use any other oil than the two recommendations (10w30 and...........eerrrr I forget, the lighter stuff,.....5w20??, whatever....but that is reccomended only in very cold climates).

Anyway, by 2 cents is to stick with the heaviest of the recomended oils. Maybe someone else has more knowledge on this than I......

And I would get Mobile 1. I drove an Old Town car 3 miles with a snapped oil pump shaft before the lifters even started to make any noise. NO engine damage at all........it is WORTH THE $$$.

07-26-06, 10:02 PM
13W40 Rotella - search it out in this forum. This is the bottom line, however.

No need for synth. Follow the cars oil change display. AC filter. Never over-fill.

07-27-06, 12:50 AM
119K is not high milage on a Northstar. It will run forever on conventional 10W30 . Many poster here have over 200K and a few over 300K on conventional 10W30.

07-28-06, 08:26 AM
If you use a syn or syn blend, just get the same recommended weight of 10w-30. As far as I know, Mobil discontinued the high mileage blend, at least I don't see it on the shelves anymore and I used to use it. Actually Valvoline Max Life is about 30% synthetic although it is not marketed as a blend.