Highest I've ever achieved with my 300SDL's is somewhere between 32 - 33 mpg.

I believe it. Especially if the environment was as described, flat and at a constant 61 mph.

Of course optimal fuel efficiency is achieved at approximately 80 km/h (50 mph) according to the European fuel consumption charts included in the owner's manuals. It is possible, according to Mercedes-Benz, that a 300SE gasser can get better than 30 mpg at that speed, but only 21 mpg at 75 mph.

I should post a scan.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)