I haven't done a full tank of city driving in the 300D to tell, but based on limited observations from partial tanks, the city mileage seems to be in the low 20's. Highway depends mostly on speed, with nearly 30 mpg at 70-75 on down to 26 at 80-85. Then there was the time I ran through a whole tank doing 85-110 most of the way-averaged 22 mpg and probably 95 mph.

Cold weather and short trips where the engine is doing more miles without being warmed up will affect mileage.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.