My 1999 SLK 230 has started using more oil than it used to and I can't figure it out. There are no leaks on the garage floor, and it doesn't smoke like an engine that needs a ring job. It really isn't bad around town, but if I get it out on the highway and drive 60-70 miles it will be down anywher between 1/2 to 3/4 of a quart. I keep tabs on it so it never gets dangerously low but I would like to know what's going on and if this signals something serious. The car runs fine but adding mobil 1 synthetic often is pretty expensive. Anyone have any ideas?

 

man, you've got all kinds of problems. the catalytic converter on cars can mask oil burning. they work well for oil burning as well as gas. you could have a sticking oil ring. do you see any oily scum build up in your expansion tank or aka water reservoir? that would indicate a head gasket or worse. you could try cleaning the varnish out from around your rings by running a quart of transmission fluid through her for a few thousand miles. DO NOT use an engine flush... you don't have the gitty-up she used to have either? is the check engine light (CEL) on? you might just want to spend the money to have her analyzed by a good trusted shop.

 

The performance is not really an issue, yet. I will check the coolant reservoir today to see if it looks scumy. The CEL is not on, yet. As to the transmission fluid flush, is there a preferrable method, ie., so many ounces in the tank per gal of gas, type/brand? As to the cat, if it is absorbing oil residue won't it eventually get clogged? And, won't the transmission fluid also add to a clogged cat? Will the trans fluid possibly activate the CEL? Also, with a sticking ring wouldn't there be plug fouling? You say It could be "head gasket or worse," like what worse? Hey, Brookings, thanks for responding. I may need more of your advice as time goes by.

 

Brookings, Water in the oil reservoir looks fine. I think I misunderstood you. You meant trans fluid in the crankcase, not the fuel tank, right? What about rislone, marvel mystery oil, or BG? Thanks.

 

OOPs, I meant water in the water reservoir looks fine--no oil.

 

put it in your oil the next time you are a quart low. this really is the best to use. it is highly detergent without breaking loose a bunch of junk all at once that will plug up your oil ports. any inexpensive ATF will work. try it again at your next oil change if needed. after that well we gave it a shot. this is a cheap try and won't hurt anything. otherwise it could be valve stem seals or a broken or sticking OIL ring. the cel is off, so the engine must be breathing ok. a dealer can look inside the cylinders and check for signs a broken ring with a borescope. how much oil does it actually use? a 80 to $120 diagnostic charge can really save a lot of head-aches. the problem is finding a good HONEST shop. check with other mb owners in your area. if you live in Oregon I can tell you where to go and who to see. luckly I haven't had very many or very serious problems with my slk yet.. once you get over 100k they can get expensive as I can testify to with my sl, that is a beauty I can't or won't part with, it's love, what can I say? I HAVE to look at her as a hobby though. there will come a time sooner or later when you have to ask yourself if it's love or the economy blues that keeps you from looking at that new black on black 08 sl550, at least a 05 or 06 slk.

 

Brookings, thanks so much for taking your time to tutor me. I pulled the plug cover last night and # 2, and #4 plug wells were nearly up to the tip of the plugs with oil! This is probably a bad/leaky valve cover gasket , right(?), that is a DIY r/r ? I cleaned everything out good and cleaned the plugs too. They didn't look too bad but of course, some carbon build up that was scraped loose easily enough. I will try the Trans fluid and stay in touch. If valve stem seals are the culprit could that account for significant increase in oil consumption? I tend to think it just might be the problem. Is this a diyer too? Head must come off, right? If its a simple head off, seals in and head back on (with proper torque) I think I can do it. Any timing or other adjustments necessary? Thank you again for your help and patience with a novice.

 

that is a real project to replace valve stem seals. I would suggest getting a subscription to www.alldata.com for what is entailed. I refer to this a lot. It doesn't cover everything but will give you an idea of what's involved, TOOLS and cost. keep in mind we are doing here some guessing of what could be wrong. I still suggest taking her in if we can't loosen up the oil rings by gently cleaning up your engine. don't let them grind your valves unless they really need it. that can mess up your lifters on older cars and why do it if it isn't necessary? if you deside to replace the seals, replace the timing chain or belt while you are at it, you probably need that too.

 

Brookings, I have removed/replaced valves in the head on an old Chevy Caprice years ago and the project went fairly well. I am sure it is more comlex with an MB but think I could do it with tips, guidance. Maybe some of the guys in my local MB club can offer some some pointers. At any rate I'll keep you informed. Thanks again for any/all e-help you have to offer. Blessings.