I recently bought a 89 420SEL with 105K. Car runs great and looks great. I had the chain, rails and tensioner replaced for preventive maintenance and peace of mind.
However, previous owner had let the car set up in his garage for about 5 months without driving it(only cranking it periodically). I just took it on a long trip (1000 miles) and the car used 3 quarts of oil. This is excessive-where should I start? Could it be due to the car not being used for those 5 months? Any advice appreciated. Thanks.

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Michael Jay
1989 420 SEL

I would look at a couple of things...is there alot of oil under the car? Maybe your seals are bad. When you start the car does a bunch of blue smoke come out of the tailpipe?<---thats usually your valve seals/guides.
If you are really burning that much oil from ring seal your compression should be low. Good luck...shouldn't be tough.

There is no smoke when I start it and no oil under the engine...Do you still think it is a seal or guide problem?
:confused:

I experience a similar situation with an older BMW. I always kept the oil topped up. Took it for a long road trip, and *wow* it needed 3 qts. of oil. What? Well the mechanic explained that if you drive only short trips, especially in cold weather, extra fuel washes down cyl wall and mixes with oil. First time you take it on a long trip you burn up the gas in the oil. I don't know if this is the correct explaination, but after replacing the three qts. my car went back to normal oil consumption.

there is a a pan under the car...a splash guard, are you sure that its not catching the oil? That is alot! of oil qt/300 miles. What happens when you go up a hill and step on the accelerator....is it smoking? If the car runs that great I would really look at those seals...you should be fouling plugs with that type of oil consumtion.Make sure your pan gasket (oilpan is intact)that can splash out oil and you'll minimal dripping

There is no splash guard...I assumed it was removed(damaged). I am not aware of any smoke when I accelerate up a hill (none visible from the rear view mirror at least). Car runs great. Should I continue driving and wait to see if any more oil is being consumed or inspect plugs and get the seals replaced? Do you think it's a guide problem? An experienced MB mechanic told me via email that replacing the seals will probably fix the problem-too early in the car's life to replace the guides (valve job).
Anyone----please comment.

:confused:

If a mechanic thinks its the valve stem seals and he is reputable... I would go for it. As far as mileage...guides can go on these cars sometimes...its unusual but possible. The problem is if that much oil is being sucked into the engine and the guide seals are gone the car should blow some blue smoke...with/guides/stem seals that is almost always on start-up. This should be an easy one for someone experienced.

Just went on a longer trip...low and behold, the car only used 1 quart in 650 miles. This is significantly better tha 3 quarts in 1000 miles however it still is unacceptable. I don't know why this happen. Thanks to the new forum on mechanics, I found a great shop in the DC area. He changed my oil and put in 20W50 and wants to see how this works out on on the next trip. To anyone-does this seem like a logical approach? :)

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Michael Jay
1989 420 SEL

For the warm summer weather it ought to be allright...I personally wouldn't use it in the winter...it would be a bit on the thick side..kinda like molasses. And I would'nt 'get on it' right away either after start up..let it warm up a little.
-Larry

I would pull the plugs.. and take a peek. All should be light brown.

If it runs well, doesn't leak, and doesn't smoke, just drive it and keep the oil full. If the guides were severely worn, you would see smoke out the tailpipes when you release the throttle and coast down from freeway speed. If the rings were really shot, you'd see a lot of smoke when the engine is under load, such as while accelerating hard. You might want to have someone follow you and watch for smoke. I would doubt, however, that a properly-maintained M-B with the mileage on it that you quote would have major engine wear. Good Luck!
Colin