My 87 300D has 240K now, and have all fluids including differential, transmission, engine, and as soon as I get time, synthetic brake fluid too!

I pride in the fact that my car's engine, and transmission, do not leak a drop! But my differential has a small leak wheeping tiny amounts. I check it from time to time but have not needed to add anything yet!

The tranny shifts OK, however there is a little flare from third to fourth before the car is up to temp. I've tried turning clockwise the modulator valve to make a more firm shift but doing so had made 2nd, and 3ed, more harsh than I liked, so I returned it back to it's previous setting. Hay, at 240K I can live with that.

Can't tell any difference between synthetic and dyno ATF! Claims are longer life, and that is why it's in there! BB