Originally Posted by tbomachines

Here are my numbers from the GPS on one of my trips. I make this trip all the time (15-20 times a year) and routinely see numbers right around 30 - this is just one example where I tracked the heck out of it. I haven't crawled underneath the car and checked the diff stamping nor have I verified the transmission. My car is a theft recovery with the speedo/odo off so its very possible I have a weird funky gearing in there which translates to better mpgs.

207 miles, GPS tracked, not odometer
Average temp 72*F (started at 77, ended at 67)
Distance measured gas station to gas station, volume measured by when the gas comes up to the brim of the fiiller neck (visual)
Gas to fill up: 6.753 gallons
207 miles / 6.753 = 30.65 MPG.

More variables:
Average temp 72*F (started at 77, ended at 67)
Total ascent: 1,538 ft
Total descent: 1,546 ft
Average speed: 61.2 mph (really good since I hit a lot of construction)
Max speed: 78.2 mph
Total time: 3:22 and 36 seconds
Humidity 81% (hit fog on the way so this varied quite a bit)
No A/C, just econ mode on the low fan setting the whole way
lights on the whole time, fogs on most of the time
Fuel was 10% ethanol (noted this)