Now that the weather herer in Massachusetts has warmed a little, the 300E is doing better on fuel. My average for the last 3 tanks (about a month of driving) is up to a respectable 22.0 mpg. The cumulative average over my first 4784 miles of ownership is at 19.6 mpg.
The effect of air temperature on fuel economy is considerable. We have had a particularly cold winter and spring. Then again, I have not had to use the AC very much. It will be interesting to see how high the average goes once we get into summer (if we have one --so far, we have had only 2 or 3 sunny days with temps in 70s or more, an incredibly dreary season).

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DavidB29
1992 300E with ASR
35 years of Diesels until now!