Originally Posted by TitaniumGero
I'm guessing these are a mix of highway and city drivers? It would probably be more accurate if their driving styles/conditions were the same. The MPG for city drivers would probably vary from traffic conditions.
True, but all I'm looking for is the long term trend. Shouldn't matter if they're city or highway drivers. City drivers' mileage will vary more widely on a given tank but over 40 tanks or more the short term variance will disappear and we'll see over the long term if their mileage is trending up, down or steady.