It seems that every time I start my car, I get a different
reading on the MPG.

Every other car I've had, including my last DTS, the MPG
Represented the ‘overall average’ miles per gallon since
new. Therefore, the MPG figure never changed much.

But, that doesn’t seem to be the case with my E350. So -
does the E350’s MPG simply represent MPG for each trip?

Why do I get a different reading each day?

jimm

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‘08 E350 Sport, P2, Black/black, Parktronic,
Voice, Bluetooth, Burl Walnut, Split rear seat,
Wood/leather steering wheel

 

There are at least two MPG. MPG one is for your current or last journey (if you are at your destination) and second MPG since reset. If you never reset your mileage counter, it would give you an overall MPG. I reset both my counters each time I fill up and that is twice a week. Inspite of the gadgetry, I use the traditional method, (Miles since reset)/(gallons filled).

 

Jimm, Check the Trip Computer menu starting on page 176 of your manual. There are two fuel consumption statistics. One continues to accumulate until it is reset. This is called Fuel consumption statistics since reset. Note that there are two sets of statistics and this one is reset separately from the other one (see page 177).

The other statistic is called Fuel consumption statistics since start. This is all the statistics since the last engine start. It will accumulate until reset or until there is a lapse of four hours since you turned the engine off.

You can accumulate running statistics for as long as you like. I use it to get the total statistics on my long driving vacations. When I get home I reset it and track my average fuel consumption around town.

Note that you can also get an estimate for the remaining mileage left in your gas tank. This should be observed as you are driving and not when you are stopped since it will be meaningless when you aren't moving. See Distance to empty on page 177.

 

The "Current" MPG can be manipulated, by either idling in Park (0 MPG then gets averaged in to the numbers the computer is crunching. The longer you idle, the worse your total MPG will be.) ...or by pressing Reset while you are driving and coasting. The Milage will be astounding & will take a while to get realistic since those high numbers are averaged in.