Questions about displayed mpg & using trip meter

[Keen4Green]

How do you guys use the trip meters A/B? Do you reset the trip meter each time you get in the car, for each fuel up, etc?

Also, is the average mpg reading (the numerical one, right?) calculating automatically each time I drive the car? Or do I need to reset the trip meter to get the current reading?

Right now I only have about 86 miles on the car. Yesterday it rained like cats and dogs and the outside temp was around 48. So far the avg mpg is only around 29-30, and it creeps up incrementally. But the instant mpg readout (the one that looks like a bar/graph) shows more wide fluctuations, sometimes in the 40-50 mpg range. How should I be interpreting the info on the two readouts?

[iamiam]

I have my "A" trip meter reset automatically on the fillup and I don't touch the "B" trip meter. In addition, when you go up 1 from the "Instantaneous MPG" screen, MID gives you the MPG from the last 3 trips.

[Mark0]

I let the Trip A reset at every refuel.
I often reset the Trip B before starting a... ehm, trip, to see what I have done this time and compare to the same trip in the past.
I also use Spritmonitor (a web service like Fuelly) to take care of all the stats, updating it at every refuel, and get an icon like this:

[Cobb]

I too have A set to auto reset and use B for testing mods. To see if there is any change, I get up to speed on the same road I take, then set cruse, then reset B to get abslute fuel economy for that run to see how mods effect mpg.

[BruceClark]

I manually reset "A" after a fill. That way, I know I can jot down any numbers I need to keep track of things on Fuelly.com - if I would let it reset automatically, I know I'd miss out on data.

[insightfulone]

Luckily the 'A' trip meter does not reset until the engine is started after the fill-up. So you can turn the ignition to the 'on' position and read your mileage etc. for Fuelly if you forget to read them before filling up.