Is 28 mpg too high? What should it be?

With the low odometer reading, still looks new - any guesses on what a fair price would be?

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K