I wish you luck in improving your mileage in your 300D, the 22-23 you're getting seems a bit low. However, please keep in mind how much it's costing to get the thing running in the 24-25 mpg range. For a 25 mile commute one-way, you're looking at a 1.4 gallon difference per week if you get from 22 -> 25 mpg assuming 250 miles driven per week.

As for considering a 240D as an option for better fuel economy, I don't think you could realistically expect much more than 27-29 mpg from a 240D with a manual transmission. Better than what you're getting with your 300D right now, but not the 32 mpg you were expecting. If you're looking for more extreme mileage from a diesel sedan, I would agree with you that a VW TDI (like one of the older jetta's or passat's) would be a better target. Or even an old late 1980's jetta.

In any case, good luck and let us know how it turns out.

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Corey

'83 240D, 190kmi