1st Mission Accomplished!

[ZOMGVTEK]

The more fuel you use, the more accurate your measurements are going to be. You really need a constant on one end of the measurements. What I do, is always fill up at the same pump at the same station, generally at night when its colder. It wont matter how much fuel you used, the pump should stop around nearly the same point every time. Using more fuel would help make this accurate. I generally run my tank 20-50 miles past the fuel light coming on, which is about 2-3 gallons left. Then I fill it until the pump clicks, record that in my iOS Road Trip fuel log app, and reset my trip ODO. No top offs, try to stick to the same pump, then it should be quite accurate.

The way you're doing things just sounds like a lot of work, and its probably not good at all for anything past a 'rough' estimate. But you don't really need a tool to calculate MPG, the pump works fairly well. Its not like a Scan Gauge is 100% accurate, you basically calibrate it off the pump.

[03NHVW]

I guess the way I see it is that all measurements are assumptions in this case; one fill up is the same volume as the next if I use the same pump at the same station, drive down to "empty" or drive to a pre-determined point on the gas guage, the guage is reading properly, the pump is actually pumping the quality of fuel it says it is....etc, whatever. Since I'm not going to drive down to the point of draining the tank and I can only fill the tank so far (I don't "top off"), and I don't yet own a SG...its all assumptions, however so far my assumed values keep producing the same numbers. 33-34 with normal driving and about 37 under "extra economic" driving. I bought this car to take some of the sting out of a 70-mile round trip commute and it has.