I drove an M110 powered beast for one year. It was a European 1985 280SEL. Quick enough, once underway.

I averaged about 20 mpg in the summer, and maybe 15 in the winter.

The 280E US engine is seriously detuned to offer up barely even 130 hp at 5000'ish rpms. Not like mine was with 185 hp @ ~6000 rpm. The 300D turbodiesel is much quicker.

Perhaps the fact that the 280E US has something like a 3.69:1 differential, and skinny tires might contribute to the poor consumption.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)