I have a 1987 300TD with the 603.960 engine. I always check the oil level a day or later after I drive the car and find that the level often varies. If it's at the 1/2 mark on the dipstick one day it could be on the 1/4 mark or the 3/4 mark the next time I check it. Recently I changed the oil and overfilled it to the 3/4 mark (I try to hit the 1/2 full mark during oil the changes) and today the oil level is just over the full mark. I will remove the extra oil as I always try to keep it between 1/4 and 3/4.

Could fuel be getting into the oil and then burning off during highway travel? My most recent trip was about 150 miles driving 45 MPH or less.

This fluctuation oil level has occurred since I've owned the car for 20,000 miles. I did have the oil tested last year and it was good with no coolant or fuel in it (possibly it had burned off when I took the sample?).

The car runs great with no problems.

Any insight would be appreciated.

Thank you,

Rick