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Cadillac Northstar Oil Leaks

Cadillac Northstar and Oil Leaks / Oil Usage

Does the Northstar use oil?

Does the Cadillac Northstar use excessive oil?  Well, No.  Yes.  Sometimes.   It depends. 

First, please consider that General Motors defines acceptable oil usage at 1 quart of oil per 1,000 miles in some references, and 1 quart of oil in 2,000 miles in other references.  So any oil usage less than this is considered normal usage, not excessive usage.

Oil Leak or Oil Usage?
An oil leak is a different issue than oil usage.  Oil leaks, blue smoke from the exhaust, or fouliing sparkplugs are signs of problems you should consider having repaired. 

Careful, Controlled Oil Usage Monitoring
In order to understand and document oil usage, the Dealer will perform an oil usage test.  During the test, only the Cadillac Dealer is allowed to add oil to the vehicle.  The oil is changed, along with the PCV valve.  Then the oil level is measured and recorded under controlled circumstances by the Dealer every 500 miles.  The test is continued for 2,000-3,000  miles.  This is only conducted on cars still within warranty.    But if your car is outside of warranty and you want to be certain of the usage level, you should track usage in the same way.

How do I Check the Oil?
This seems like a simple question, but to be exact we need to follow a few steps:
Make sure the Cadillac is warm, up to operating temperature.  The oil level can change due to the temperature of the oil, so we want to maintain that as a constant.
Park the Cadillac on a flat surface.
Wait 2 minutes after turning off the engine to ensure the oil has settled.
Check the oil level via the dipstick.
The oil level should be between the marks on the dipstick.  The marks on the dipstick are 1 quart apart.  Record the oil level.

The low oil level warning will go off in the Cadillac at 1.5 quarts below the low line.

What do I do if my Northstar is using oil?
If the Cadillac is still under warranty, please consult with your Cadillac Dealer.

If the Cadillac is not under warranty, carefully measure and consider the level of oil usage you are experiencing.  If the oil usage rate remains constant over time, it may be a good economic trade to simply continue to add oil as needed, and otherwise maintain the Cadillac as normal.

If you decide to have the Northstar rebuilt or replaced, the approximate costs can be as high as $4,500 for a rebuild, or up to $10,000 for a complete replacement by a Cadillac dealer.  This equates to a lot of oil, so many owners who do experience oil usage simple monitor it to ensure it is constant, then add oil as needed.

What about adding some XXX aftermarket product which claims to prevent oil usage?  Well, no, don't do that.  Cadillac does not recommend that you use any oil additives.

What can I do to decrease oil usage?
WOT.  What, you say?  WOT = Wide Open Throttle acceleration runs.   One theory on Northstar oil usage is that carbon build-up on the piston rings can contribute to oil usage.  Many customer oil consumption complaint engines have been torn down with absolutely nothing wrong found.  The engines are often reassembled and put into test cars and driven by the engineers and more often than not the high oil consumption does not repeat itself.  By repeated WOT runs, one can ensure that any carbon build up on the piston is cleared out and kept clear, and that the rings seal properly.

The proper WOT procedure is
1) Fully warmed up engine on highway that you can vary your speed on
2) Tranny in 2nd gear
3) At 40 mph, WOT to 70
4) take foot off gas and allow the tranny gear to slow the car down to 40
5) repeat 10 times

An last, but not least, air the engine out frequently. It likes to be used and red-line upshifts at WOT help promote clean combustion chambers, exercise the piston rings to keep them free of carbon buildup and keep them mobile and to ensure the engine is broken in and maximum sealing is obtained. The Northstar does not like to be babied around. It likes to be run hard frequently with a WOT blast in merging or whatever.... Even engines reported to use 1 quart per 1500 miles tend to improve to 2500 miles per quart or better when subjected to a regular schedule of use and "abuse"...

Also, your Dealer may offer a top-end engine cleaning procedure.  This does not appear to be as effective or economical as WOT runs.

Another tactic is to keep your oil level at the low end of the scale.  Oddly, the more full the oil level is, the more likely oil usage will occur.  Excessive oil will be pushed out through the PCV system.

Use conventional, mineral oil with the Northstar, not synthetic oils.  Synthetic oils appear to be more likely to promote oil usage in this engine.

Why Does the Northstar Engine use oil? (when it does)

The majority of owners don't experience excessive oil usage. 

However, for cases where owners do experience excessive oil usage, there are some characteristics of the Northstar that may contribute to oil usage.  

It is not unusual for a Northstar to use more oil than some other engines. It is a high performance engine and has to allow a little more oil to the top rings for lube as as well as down the 32 valve guides.

The Northstar uses low friction piston rings in order to minimize horsepower losses to friction.  The advantage of this approach is added power; the disadvantage is a lessened efficiency at recovery of oil along the walls of the piston.

The Northstar uses a very agressive cylinder bore hone.  The advantage of this approach is good oil retention and distribution along the cylinder walls for  cylinder cooling.  The disadvantage is lower efficiency at recovery of oil along the piston walls.

Carbon buildup in the rings and ring sealing are also variables that come into play with break in, operating schedule, type of oil used, etc.

The Caddyinfo Discussion Forum  also has additional information on this topic.