1996 Cadillac Deville

[Ando1985]

Hello all, brand new here... I have a few questions about my car! I have a 1996 Deville with the 4.6L Northstar with 54,000 KMs on it, I just purchased it with 49,000, two owners both older gentleman, very well maintained vehicle (see babied). The car had synthetic 5W30 in it, I had the oil changed as soon as I could at the local lube shop which offered me Synthetic Quaker State 10W30. The car has burned about four litres in the past 5,000 KM with this oil. I know the Northstars are notorious for burning oil but this seems like a bit much. I am also aware WOTs on this vehicle are necessary to keep oil consumption in check as well and have been performing them as often as I can.

I was wondering what type of oil you would suggest for my vehicle, or anything else you can suggest to keep the oil consumption in check. Keep in mind I'm in Southwesten Ontario and it is going to be quite cold for awhile!

Thanks in advance for any feedback!

 

[J. A. Rizzo]

I also had a 96 Northstar. It burnt about 1 qt. per 1000-1300 miles no matter what oil I used. Given that the sump is 7.5 quarts and it does burn a bunch of oil, I would use a decent 5W-30 like PYB or QS or Havoline or Motorcraft, add a quart when it gets a quart low, and change every 6000-7500 miles or follow the OLM if it has one. I knew some people who also said they burnt less oil with regular Rotella 15W-40, but in Ontario winter, I would stick to a 5W- or 10W-30. With all the oil these things burn, the additives are kept renewed pretty well just by keeping the sump full across the OCI. A synthetic is way overkill, very expensive, and unnecessary especially for this engine unless you're going to extend the drain interval out to 12k or longer based on UOA results that include a TBN reading.

You're right about the WOT. Also consider checking and changing the PCV valve if needed, and once in a while dropping it into 2nd, running up to near redline, and letting it coast back down to 2000 RPM or so a few times (in a safe place!) like the old Italian tune-up. That helps keep the rings moving under high vacuum and blows out deposits.

 

[Ando1985]

Is it possible to return to a non-synthetic oil? I wasn't sure what to do when I took it in for a change so I stuck with the synthetic, I was under the impression that synthetic was overkill but wasn't sure if it would be more harm than good to put something that wasn't synthetic in there as I'm not sure of the exact history of what oil has been in this car.

 

[Slippery_Pete]

No harm in going back to dino.
Being that the engine has likely never seen the redline, that is the first ting I'd do. every once and a while N* engines need an Italian tune up.

P.S.

 

[Ando1985]

Thanks! Good to know, its seen the redline a couple times now... I'll take it back to dino on my next change, it's been 5000K since a change and the OLM reads 54%, from what I hear it'll be safe to keep it running for awhile before I change back. Thanks a ton for the welcome and advice, anything to add would be appreciated as well!

I make long trips of 200KM two or three times a week with occasional city driving in between, about 70KM

 

[ronrackley]

Originally Posted By: Ando1985
Thanks! Good to know, its seen the redline a couple times now... I'll take it back to dino on my next change, it's been 5000K since a change and the OLM reads 54%, from what I hear it'll be safe to keep it running for awhile before I change back. Thanks a ton for the welcome and advice, anything to add would be appreciated as well!

I make long trips of 200KM two or three times a week with occasional city driving in between, about 70KM


A lot of owners have put up with adding oil regularly to Cadillac Northstars that were otherwise fine engines. Some time after 2001, the piston rings were supposedly changed to cut down on the burning of oil. Some time before 2000, the design was changed to reduce the leaking of oil. The 2003 and 2005 I have now use very little oil. The 2000 and 2001 that I had before used a fair amount. The old ones from the 1990s often both burned and leaked oil and got less than 1,000 miles to a quart and ran just fine that way indefinitely as long as oil was added on time. A few quarts of oil a year cost a lot less than the thousands of dollars in cost for pulling the engines to work on them. Running conventional oil helps reduce leaking. I'd try Rotella 15w40 and see if it is OK for cold starts.