John,
I used the odometer & the fuel pumped in. I agree 2 decimal points is probably pushing it but over 45k and 6 years the weighted avg should be pretty good. The main thing for me is if it goes down then something is wrong.
I have never had a Morgan with a good fuel gauge. I use instead distance traveled & refill after say 200 miles. The Brooklands is a real pain to totally fill the tank & only some petrol pumps seem able to go slow enough to totally fill it, after 2 clicks on the pump you can get 8 -10 l more in if you have the right pump , time & patience. However the mpg read out seems very close to the weighted average. After 4279 miles since I bought it in Sept the weighted avg based upon the mpg readout is 25.6, the weighted average based upon fuel pumped in & miles is 25.5. There are due to covid not many long runs in these numbers. The best seen was just under 30 mpg.
I have used a GPS app to compare the trip to a GPS mileage and they are very close.
