Northstar Engines and System Technical Discussion Discussion, Oil Question????? in Cadillac Engine Technical Discussion; Ok. I bought my 94 Caddy SLS in april with 113,000 miles and changed the oil at the 114,000 mark. ...
Automobile(s): 94 Cadillac Seville SLS, 88 Cadillac Deville, Trailblazer SS
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.
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 $$$.
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.