My car may have a drinking problem.

My '06 MC 5sp. has used (or leaked) 2 quarts of oil in the last 4500-5000mi. I have had it to the dealer twice now. The first time was after using a quart in 2500 mi. It was discovered that the oil pan gasket was leaking, there was no fouling of the spark plugs and no other leaks were discovered. The gasket was replaced under warranty. No big deal.

Fast forward one month and 2000 mi. I check my oil and find that a quart is missing. Another trip to the dealer. A wet and dry compression test is done and nothing is found to be amiss. Spark plugs are checked again, with no evidence of burned oil. The top and bottom of the engine checked. No leaks. The tailpipe and rear bumper are checked for oil residue. Nothing. Coolant tank and radiator checked. No oil. The service rep tells me that they cannot find anything that would indicate a problem and does not want to tear into the engine to try to find anything (now out of warranty). He asked that I monitor it and see where this goes. Not the best answer, but one with which I cannot argue.

I have not seen any oil on my garage floor or under the car when parked elsewhere. Have not seen any blue smoke on startup or hard revving (did this in the garage to check for anything obvious). If the oil is not escaping the engine by dripping, or getting into the combustion chamber to be burned, or ending up in the tailpipe as blowby, where is it going??

Had the oil changed by the dealer for the first 36000mi and then DIY for the last 14000. Went with the OBC interval while under service warranty and at 7500mi when DIY. I did switch from the Castrol the dealer uses to Mobil1 full synthetic when I started changing it myself. Have averaged 33mpg with mixed driving.

Any ideas????

 

Maybe accumulating in the Cat?

 

Wouldn't it get burned there and exit the tailpipe??

Best idea I've heard yet, though. Thank you.

 

in the coolant? the stock oil cooler can break internally and mix oil with coolant.

 

Are you driving it harder than normal? I burn alot of oil when I'm lead-footing it. Don't burn hardly anything when I'm on my meds and driving like a sane person.

 

do not have an oil cooler (to my knowledge, there could be a kryptonite mouse shield in there for all I know), but they did check the coolant and no oil there either.

Yes, admittedly, I do drive like a maniac at times (and I am, in all seriousness, on meds for that kind of behaviour. and not only automotive), why have such a fun car and granny it. Hard corners, "brisk" acceleration, are on the menu for "Nigel" on an almost daily basis. My quandry lies with there being no real evidence as to where the oil is leaving. I feel a little better knowing that there is, at least without an engine teardown, no evidence of engine problems, but I still want to know where the oil is going.

Time to set the oil-elf traps in the garage, I guess .

 

it's not under warranty anymore ? this is important cause a crap dealer will say anything to run the warranty out. if not under than i'd say you've done it all . btw it does have a cooler/exchanger at the back of the block . below the filter housing .

 

Wow, wasn't aware that it had an oil cooler. But then again, I do refill my blinker fluid on occasion .

It was under warranty the first time time I brought him in (48,500mi) and is now over 50 and out. The service rep told me that if the problem can be identified it would be a pre-existing (i.e. warranty) condition since I brought it in the first time before the expiration. Problem is pinpointing a problem (from our department of redundancy department).

For now, I plan to keep an eye on the dipstick and see where this goes. Not much else I can do at this point and I am loathe to take it to an independent mechanic who will probably find the same thing the dealer did. Or tell me I need an engine rebuild, which I doubt is true.

 

I don't know much of anything about Mini's, but I understand that cars w/ minor cases of ring blow-by can go through oil without many of the old standard signs.

The explanation I've heard is that, if your driving w/ the Cat at optimum temp, it will burn the oily mist pretty thoroughly for a while. Then, as the Cat sacrifices itself, you'll either have a big performance problem or you'll see the smoke.

I only thought of it because you've pretty well eliminated the usual alternatives.

Best of luck.