Why do you say the 240's get so low?? I thought even 300's should generally get above 30. My 240 got much higher. I also lived in an area which was quite hilly at the time, which isn't the case now. The 240 sucked on hills, but mileage was good. I have new fuel and air filters, brakes don't drag, I recently checked/adjusted valve clearances (they weren't much off to start). Don't know how good the tires are for efficiency but they're Bridgestones and less slippery in rain than some of my other cars' tires though not as good as the set of Michelin Weatherwise's I have (I suppose better traction means worse mileage). A/C has a broken line in the 200, so it's never running, however if I switch it on it bogs down the engine so I don't think the belt being attached is an issue in general. Could it be that because I didn't do much maintenance on the 240 that it's fuel injectors ended up more clogged thus getting better mileage or something? Or maybe a previous owner had tuned it somehow? The 200 has a 3.92 differential - I've been thinking of putting one from a 240 on it which is a bit lower. How do you differentiate fuel quality/type? There's never more than one option for diesel at stations...