After owning my 240 Euro for several years, it is interesting that I should only notice this now. I don't drive it much in the summer because of its Euro air conditioning. While I was driving out of town yesterday when the temperature outside was about 101 degrees, after 40-50 miles, I would notice the oil pressure fluctuate off the 3 peg while cruising about 60-70 mph. It would flutter sometimes and then peg out a while and then it would slowly drop down to 2-2.5 and then peg out again while at constant speed. Water temp was normal and rock steady, no valve noise or anything. When I would slow down to a stop, the pressure would drop down to .5 bar while stopped in gear. This was the lowest pressure that I've ever seen with this car. Oil level fine, doesn't burn any oil, and this is an 85,000 mile motor with good mx history. When allowed to cool for a few minutes, the oil pressure at idle was back to its normal hot idle of 1-1.5 bar and pegged at any higher rpm.

OK, this is my first question. Is this like any oil gauge failure that anyone has seen? Or, this is my theory, since this is a Euro and does not have an oil cooler, am I seeing the limits of the high temperature operation of the Euro model? I am using Mobile 1 5w-40 left over from the winter. Would 15w-50 be far more appropriate for the summer?

Tonight, I changed out the Wix filter with a junk Indian that I had in my inventory. I also replaced the o rings of the filter stem and blew out the little passage through the stem with compressed air. I drove it tonight and all was normal, but it is only in the 80's tonight.

I appreciate any input on this. I really don't think that there is any reason to believe that the engine is worn or shelled out and I know that the logical thing to do is hook up another mechanical guage to verify the pressure, but I'm floating the theory that 5w-40 may not cut in in a Euro in extreme heat. I guess I could just change the oil ...............

Thanks for listening!

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'82 240D Euro 68K and growing

i dont think the 5w40 is listed as an oil weight recommended for that car.

the fluttering thing is troubling to me. does the pressure fluctuate while holding a steady engine speed?

in 100 degree weather i would want an oil cooler if possible.

possibley just using a heavier oil may do the trick.

i have never heard of an oil pressure guage failing, anyone else?

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.