I recently replaced mu 2006 STX with a 2010 STX. This one has lots of bells and whistles that I did not have in the old truck. One of them is the message center that gives "Miles to Empty" and "Average MPG". I believe there are 2 fuel tank sizes, 26 and 36 gallon. Although it is not listed on the window sticker, I certainly have the 36 since it takes 30 gallons at a whack. But I digress.

Here's the scenario: I fill the tank, set the Trip B counter to 0 and reset the average MPG display. If I drive, for example, 340 miles and the MPG readout says 17MPG, it would stand to reason that it should take 20 gallons to fill up, at the same pump. It invariably takes 10-12% more fuel than it should, so I'm a little baffled as to how the MPG is calculated, because it does not have much basis in reality.