[brucepick]

I'm sorry to say I think you will need to get past your distrust of pump gallons data. That's because you will need to calibrate your MPGuino after hooking it up. And guess where you get your actual gallons data? Yup, the pump display.

Read some of the threads on fill technique. Briefly: consistency is the key. Same station, same pump. I try for same time of day (roughly) because gasoline expands considerably with temperature increase. Same squeeze pressure.

As for myself, I squeeze about 3/4 until about a gallon short of full. Then I relax to a pretty standardized very slow rate till it clicks once. Check my Civic's gas log over recent months and you'll see notes of actual fill vs MPGuino estimate. Very close.

And BEST OF LUCK wig the highway mpg quest. I've been on a similar path for some years, with a current commute of 55 mi each way.