Relationship of Oil Usage to Change Interval
 

Is anyone able to speak to the relationship of oil usage to oil change interval? If a car is LEAKING oil, that, if anything, would lengthen the change interval (since the leaking and filling represent a succession of mini oil changes). But, one time when I was listening to the Car Talk guys, they made the point that when a car is USING oil, you should actually change the oil MORE often than you would otherwise. But I foget their reasoning. Anyone know what the logic would be?

Thanks.

Leaking oil removes what is ever typically in the oil as well as the oil. Burning oil typically removes the lighter components of the oil mix, leaves the soot in the sump. Adding make up only dilutes it a little & gets the concentration of soot etc back close to the pre burn level.
The oil in an oil burner decomposes quicker as the combustion products from the oil burning partly go into the oil.

Thanks...that's helpful. While I'm interested in the general question for my Benzes, my immediate concern is my daughter and her 93 Honda Civic. She's apparently burning about a quart every 1000 miles. She's using Mobil 1 and I originally recommended 7500 mile drain intervals....wondered if that should be shortened.

By contrast my 92 300D uses not one drop over the course of a 10,000 mile drain interval.

I think gassers are a little different. They dont have the same soot in oil problems. A little civic doing a quart in a thousand sounds like a motor on the way out. sorry to give bad news.
If she is mainly doing short slow runs, I would be thinking every 5,000 may be better. Going up one grade in viscosity can sometimes help.
You could always do the "good dad " thing & do something about the motor or maybe the car!!! ~ some how I suspect you would like to do that any way!!!! :)

Ha! I did the "good dad" thing by letting her use my SDL when I had it and then my 92 300D. I love her with all my heart....but, automotively, she's on her own (although she still gets my free, at times unsolicited, advice). :D

Burning oil means rings are bad, and therefore is more blowby of combustion gasses into the crankcase & oil, needs frequent changes.

Leaking oil doesn't really extend the change interval, the filter is still to be considered.

..and / or the head is worn (valve guides)

I don't want to start one of these huge discussions. I have a 2006 E320 CDI with just a little over 80K. I have used Mobil 1 since new and have changed it "by the book" every 13,000 miles. I have not used a drop of oil in any of the intervals. In fact I had an oil analysis done and the oil report came back with numbers almost equal to new oil -- of course there was soot in oil and some of the parameters did change a little-- but nothing to write home about.

I agree that the lighter components of the oil will burn off first and leave a little more sluge-- ergo you need to change it a little more often. I don't know if anyone has experienced this but sometime just changing the brand will eliminate oil consumption -- going from Penzoil to Shell -- just a thought

3pointstar

It would be nice to know the Engine Milage and if the Engine at one point or another was over heated (overheating can glaze the Cylinders).

If not from leaks Oil consumption could be caused by Valve Stem Seals. More so on a Gasser due to Vacuum in the Intake Manifold.

Gas, Engines can also suffer sticky Piston Rings if it is driven on a lot of short trips and the Engine never gets to Warm up; or the owner does not worm the Engine a little before driving on short trips.

You might try that Marvel Mystrey Oil soak just as has done on the Diesels; to rule out the posibble of sticky Rings. It is cheap to do.