Originally Posted by tmnCA
Why would the dash readout be inaccurate? It knows how much fuel has been used roughly if the car is on a level surface, and it knows how far you travel in the measured time. Any inaccuracies in the fuel level due to non-level surfaces would average out in time, it should be pretty accurate. The information on the display is a current average from the last reset while fuelly/manual calculations are based on the last fill-up.
I ALWAYS reset the average mpg meter in the car when I fill up the car, at the same time calculating the average mpg manually (my fillups take a very long time). They should theoretically be very close, but in my car they are not. It's annoying, I wish the dash was more accurate, but at least in my case it is way off, by as much as 10%. Sometimes it is more accurate. I have not been able to figure out under what circumstances. I thought for a while that it was because some gas stations will pump a little bit more gas in after the pump clicks off. But the last 2 gas tanks I made sure this was not the case.
Bottom line is personally I would not trust the "Distance to E" on the dashboard UNLESS my manually calculated average MPG was identical to the average MPG on the dashboard since last reset. There may be something else going on that I am not aware of. If I figure something out, I will let everyone know.
'02 Honda S2000, 2012 Silver Focus HB, 5 spd Ordered August 13th, Build Date Sept 19th, delvrd: 9/29/2011. Sport pkg, Moon Roof, Winter Pkg, 203A