Since I don't have the NAV system in my Escapes, I use the odometer and pump method. Sure, you will get some variations from tank to tank but ultimately you still get total miles driven and total gallons of gas purchased. The former over the latter gives you a darned good figure for lifetime mileage.

I use an Excel Spreadsheat to track my mileage and on both Escapes after 4 or 5 tanks you could see the plot of lifetime mileage approach where it is now and pretty much hold there. The individual tanks vary quite a bit but the lifetime average mileage stays pretty flat.

And anyone who thinks there isn't a competition going on here - I remind my wife all the time that she is killing the mileage in the '05 since she started driving it. See the numbers below, you'll see. She's learning though....