Friend's Cadillac, 32V Northstar, 180K, Opinions wanted...

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Apr 11, 2003
Spring HIll
Friend of mine just purchased a 95 Cadillac with the Northstar 32V engine. Car is in excellent shape, I think the previous owner did 3K OCIs, no idea what oil they used... I mentioned that an AutoRx treatment using cheap oil and SuperTech filters, then running Amsoil for 8-10K runs would provide long life without needing to rely on 3K OCIs. He's heard of Amsoil before and really wants to use it and would love to free himself from the 3K OCI, too. What viscosity should we use for this vehicle? He travels mostly 20+ mile trips to/from work. Some are long distance hauls. How does that all sound?
If you really want a synthetic for this engine? The Amsoil "ASL" 5w30 and 10w30 are awesome oils. A counter-question from me to all is do you think the 2000 series OW30 would not be recommended in a high mileage v8??? (I would not have him spend on the 7500 series, as he seems to want a synthetic of the same caliber as Mobil1 or so)
There is a fairly recent post on this site about a driving procedure that cleans the rings on the Northstars. Probably well worth reading.
Tell him to drive it carefully, and if it ever overheats, sell it immediately. I bought a 94 DeVille Concours with 158,000 on it. 2,000 miles later, and fortunately still under warranty under Massachusetts law, it cracked a head on me. After reading up on the motor a bit and discovering other people having the same problem, I've decided that the Nortstar really isn't a long life engine. I loved that car while it lasted, though.
Alright, I'll sideline the idea of 7.5 qts of Amsoil being wasted due to leaks and such, would a run of AutoRx be adviseable? ...or just change the oil every 3K and pray the engine lasts a long time?
yeah my friend had a cadillac with a northstar. I asked to take it out for a spin. My first impressions were awesome this car really runs SMOOTH, smoother than any V8 i have ever seen. Mileage?? 100,000 on the clock, with regular oil. Took it out for a spirited run, FLOORED it, then it made a noise and the check engine light came on, brought it back and pretended nothing happened. I guess Northstars are good for grandpas who drive it easy all the time, but for me i like to drive fast. My audi seems to take it well [Smile] hehe
My wife has a 95 STS with fairly low mileage. It hold 7.5 quarts, but it's common for the split block design of the Northstar to leak. It may do it with any oil. She just put the dealer Mobil Blend in it and it seems fine. I run synthetics in everything, but the Northstar just gets the Blend. It leaked @ 40K, not a lot, but I afraid some syns would make it worse and be a needless expense in this engine anyway. It's my last oil of choice but, the Mobil Blend seems fine for this particular car.
Oh, we've had the car since 96 and it's great. I just wanted to tell you about this leak problem. GM techs are quite familiar with it. I wouldn't want you to spend for 8 quarts of an expensive synthetic and then blame the oil company. It is a potential problem on these Northstars.
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