I took a small trip about 125 miles of highway driving at 65-75 mph. The car is a 1983 240D with 63,000 miles on it in good condition. It was a hot day 83+ degrees. After exiting the turnpike and stopping for a light, I noticed that the oil pressure gage was fluttering on or about the number 2 on the gage. It normally stays on the 3 which is the max when at idle in local driving and at idle. The water temp stayed on a constant 80C highway and local driving. The fluttering is in concert with the rhythm of the engine. As the car is shut down even for a short time the pressure returns to the normal 3 at idle without the flutter. It seems to me that the oil gets too hot and thins too much at highway speeds and returns to normal as it thickened during local driving. The oil being used is Mobil-1 EXTENDED PERFORMANCE 15W-50 with maybe 100 miles on it since the last oil change. My question, is there damage being done by the oil or is there a minor fix? I'm thinking the small rubber gaskets in the oil filter might leak the pressure at higher RPMs and therefore result in the pulsations of the oil pressure at idle. They have never been changed, I am the original owner of the car.
My second problem occurred at the same time. I pushed the trip meter on the speedometer because I wanted to check the fuel mileage on this trip. I haven't ever checked it and am curious per the recent discussions on this list. After it registered 100 miles it stopped registering. The speed needle is working fine so I did not notice when the gage stopped recording. The total miles odometer stopped recording also at that time. When I noticed the problem I clicked it back to zeros. It still doesn't record, any suggestions? Thanks
