Cadillac Northstar Engine Woes and Fixes
I was using Amsoil 15-40 heavy duty marine diesel synthetic oil. It seemed to lesson the oil burning but the leaks persisted.
I then found Auto Rx and as per instructions switched to conventional dino oil. I run Chevron 15-40 diesel oil or Castrol 20-50 motor oil. I went the route with the RX and did one bottle the first time as I was nervous. After running it and changing to just oil, I noticed the leakage had cut way back. I then ran the RX again with a double dose of two bottles and noticed the oil leaks had ceased 100%. Next oil change was with no RX and the leak started again but not as bad. Next oil change I used one bottle of RX as a maintenance does and the leak is negligible. I've experimented back and forth between conventional oil and synthetic oil both with and without RX. I've even tried 6qts of conventional and 2 qts of synthetic and it leaks. For some reason the synthetic gets past the seals.
With synthetic oil I get leaks even with two bottles of RX. With Dino I get none with RX. The car has 110k miles and I do change oil frequently.
I had written about this on the NorthStar board a little over a year ago as most people with a used NorthStar cannot afford to replace the seals. GM has since changed the material of the seals. I believe it was the crank case half seals and/or oil pan seals.
I did not realize the engine was designed to burn oil when I purchased it. I would guess it used one quart in 600 miles when I first purchase it and now is 1,000 to 1,500 miles. Interestingly it burns less with synthetic than conventional. I never have seen blue smoke, only black so I'm not sure how and when it burns it off. My oil still is clean at 5,000 miles but I change it anyways.
I am also using the RX in a Volvo 240 and E305 diesel one ton. The only leaks I see now are from the power steering pump which is notorious on the Fords. Also using it in a 10hp snowblower but since you are in Florida you have no idea what those are used for and won't believe me if I tell you!
I have no explanation or theory. I'll be doing another oil change in the next few weeks and will go with one bottle and straight conventional to monitor. I like using a little synthetic for the ease in starting in the winter but will hold off to let you know.
Thanks
Charles Bennett
Chambersburg, PA
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