Northstar Oil Consumption

[rickp]

I have a 99 STS with 60,000 miles. The oil consumption seems high to me, over one quart per 3,000 miles. What is the normal range people are experiencing?

I tried a search but the 'engine' won't accept a 3 letter word. What else could you do to search for a topic on "oil"?

[Brett]

what you're experiencing seems pretty reasonable. I'm sure a few others will chime in as well though

[Eldo1953]

You might do better with this tech question in the Northstar Tech board, I'll move you there.

[jadcock]

One quart in 3000 miles is well within spec. The actual tolerance limit is one quart per 1000 miles. This is due to the aggressive and deep hatch pattern on the cylinder walls, to promote good high speed oiling. Downside is increased consumption over a "normal" design. Upside is you'll probably never have to have your Northstar oversized due to cylinder wall wear.

Some engines use more than others -- this is due to the depth of the hatch lines in the cylinders. New stones are installed after every so many engines have passed through the machine. There will inherantly be a variance between the first engine on a set of stones (deep hatching, very good oiling, most consumption) and the last engine on a set of stones (moderate hatching, still good oiling, least consumption). Sounds like your engine was towards the middle of the pack. Mine is too -- I use a quart about every 2000-3000 miles. I also run the snot out of it regularly -- and that adds to the consumption as well (makes sense -- more rpm = more oil consumed).

[rickp]

Thanks people. I feel better now. Seems strange though that this rate of consumption didn't happen till fairly recently. That is why I thought something was recently wrong.

[jadcock]

That's odd. How do you drive the car? Is it mostly at light throttle (just cruising around), or do you run it up to redline a few times a week? The rings like higher speeds to keep lubricated. It's conceivable for the rings to stick if the engine is constantly driven below 2000 rpm or something like that.

[rickp]

I drive mostly commute on surface streets. A couple times a week on the freeway for 20 minutes or so. Light demand on the engine I would say.

[jadcock]

I'd suggest doing some 20-80 mph full throttle runs to blow all the junk out of the engine. You'll probably notice a lot of smoke out of the tailpipes, but this is good -- you're getting any carbon/caked oil out, and making room for good lubrication again. This may unstick the rings, if they are indeed stuck.

Then again, 1 qt/3000 miles is a pretty average-to-good rate for a Northstar -- I wouldn't do anything other than doing a few full throttle runs to satisfy my curiousity. Other than that, you probably have nothing to worry about.

[rickp]

Thank you much. Sounds like good common sense advice. Will do and, I will print this up for the arresting officer, should there be one! :- )

[ljklaiber]

For what it's worth , my 95 sls gets run hard quite often, and at 138K miles it uses 4 to 6 ozs per 200 miles when I change oil and filter.