I have an 89 300 se with 170k miles. When I ran 10w30 oil, and take it on a long trip, within 1.5 hours, my oil light would come on and the dipstick would show low oil. I changed to 10w40 and the problem got a little better, but still consumes about a half quart every 3-4 weeks. I notice any smoke from the exhaust when the car is driven. I do not notice any leaks in the garage. Can anyone tell me where the oil may be going? I know it is normal for an older car with that many miles to use a little oil, but is this normal for mercedes? This is the first I have owned.

Been there, done that.

In my case, the head gasket had developed a leak. While the head was off, new valve stem seals were installed. I think it was April of 1989 that 103 motors got improved valve guides.

You could be looking at new guides and stem seals.
I was using a qt. every 1,000 or so. I changed oil about 1,200 miles back and have lost no oil - big improvement. My vehicle did not smoke before the surgery. It's nice to once again have a car that's fairly oil tight.

Hello,
At the very least, the valve stem oil seals need to be replaced. If your car has a catalytic converter, you will not see the tell tale *oil burning* blue smoke from the exhaust.

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Nachi11744