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My '09 C350 is losing a quart of oil within 500 miles. No apparent leak. Car is well maintained. Exhaust smoke looks ok. Passes smog inspection without any issue. What could be the problem?
My '09 C350 is losing a quart of oil within 500 miles. No apparent leak. Car is well maintained. Exhaust smoke looks ok. Passes smog inspection without any issue. What could be the problem?
Consider though that 229.5 was created at a time when inferior oil spec existed. If you think you have a dirty valve train, Try using 5/30 Restore and Protect. It's cleaner than anything that would have been available when the specs were written for your car. I say this after using it in my 275k lx from 06 and can its a good oil. I do short 3-5k oci on that car as well and it's spotless. with zero consumption ever. That, or like Cali said, use something even heavier like motul fs 5/40 for a slower clean with regular intervals. Personally, a mild engine flush is also ok if all cautions are heeded, meaning if your engine is sludgey, you want to clean it slower...
Last edited by Baltistyle; Mar 23, 2026 at 06:05 AM.
Consider though that 229.5 was created at a time when inferior oil spec existed. If you think you have a dirty valve train, Try using 5/30 Restore and Protect. It's cleaner than anything that would have been available when the specs were written for your car. I say this after using it in my 275k lx from 06 and can its a good oil. I do short 3-5k oci on that car as well and it's spotless. with zero consumption ever. That, or like Cali said, use something even heavier like motul fs 5/40 for a slower clean with regular intervals. Personally, a mild engine flush is also ok if all cautions are heeded, meaning if your engine is sludgey, you want to clean it slower...
I have used R+P with no issues. Stopped an oil filter housing leak too. Our cars are old enough that their "back end of the bathtub curve" status warrants careful deviation from the original MB standards.
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