I'm curious about the methodology for computing the average fuel economy for each model, on the main graph on the front page of the "compare" tab. Are all the tanks from a particular model averaged together, or are the lifetime MPGs of each individual vehicle averaged together? I believe these two methodologies would produce significantly different results.

If you average the lifetime average MPG of all the vehicles in the database together than every vehicle will have the same influence on the average, despite the number of tanks entered, the number of miles on the car, etc.

If you average all the tanks entered into the database, the individual vehicles with more tanks added into the database will have a greater influence than the individual vehicles with fewer tanks entered into the database.

The cars seem to get the worst mileage when they are brand new. The dealers often don't fill the first tank all the way up, leading to a low first tank. They seem to break in over the first several thousand miles and get better mileage. They seem to get better mileage after the first oil change. They get better mileage as the drivers learn how to drive them.

Many of the cars in the database have very few tanks. People probably log in here when they first purchase, enter a tank or two, then lose interest when the "newness" wears off.

If you are using the "average of averages" methodology I think this may lead to an unrealistically low number.

Whoever has access to the raw numbers, can you run it both ways to see what the difference is? I'm kind of a nerd I guess, but I'd really be interested to dig into the data a little deeper and see what I can find.