Not your imagination.... its the diesels that are drivin like old lady cars that suffer the worst problems. Worst thing you can do is never heat the car up and bottom all the gears at low rpms.... then combustion chambers get fouled with carbon, kicking unburnt fuel and turning into a slug.

Hell yes, these cars love to run all day long and 300 miles is just walk in the park for them. You probably also noticed immediate rapid start if you stopped at any time during your trip.

Regarding checking the oil level, most folks agree that MBs seem to use oil most at the topped off level..... thus many people keep them 1/2 or 1/3 qt. down all the time where oil consumption seems to taper off.