After highway driving, I still like to follow the habit of idling my 3.0d for about 3 -5 min.

Regular oil changes will also help.

I also could not believe how dirty my air filter was when I replaced it two nights ago. It was a miracle that the engine was still running. There were all kinds of debris clinging to the outside of the filter. I truly do no believe bmw's policy of changing the air filter after every 100 000km, can be good for the engine.

just my 2c