My 89 260E has been getting progressively worse gas mileage. I suspected the transmission may not be shifting correctly. I had the ATF and filter changed a couple days ago. The filter was clogged. There was no debris in the fluid. Seems to be better. My question is how many times should it shift? Accelerating slowly, it shifts at ~20mph around 2000 rpm or even a little less. It shifts again at 25 or so mph at the same rpm. It doesn't shift again. RPM at 65mph is a little over 3000rpm. The gear selector has 2,3, D, so it would seem two shifts are correct, but I drove another car with the same shift numbers on the selector, but it shifted 3 times. That car was a little newer 300CE, so maybe a different transmission.
I have read other posts regarding using something that may help rid build-ups and then replace with synthetic ATF. Is this something to do with a high mileage transmission?
Many thanks to all. I have been read this site for some time and only decided to register today to ask this question. (And I have a couple more.)