(This would be for after the EPA thing is settled)
In LA they have had Toyota Prius add signs showing the real-time gallons saved. Why not one for GasSavers? Here's how it would work :
1 - In the middle of the night you would fire up a shell script to gather the latest Gaslog entries into the system. Each entry would be compared to the combined EPA MPG entry for that car in the Garage.
2 - The gallons saved or lost (gotta be honest here!!!) would be added to an aggregate total for the day.
3 - The total would be used in a little Java(script?) program that would have two inputs, the running total for all of the days up until now and the new total for that day. As the day goes by the program would look at the computer's system time and update it's little "gallon's saved" meter. It could be a slowly running gas pump, similar to the one you already have in the upper left corner. For example, if the new total was 240 gallons, then the meter would show the "Running Total + 10" gallons at 1 AM and "Running Total + 100" gallons at 10 AM.
Notes : The program would have to be run at least once for the whole data set to generate the initial running total for the site. The "gas clock" would be depicting gallons saved from the previous day. Some days it would run slow, others maybe a little fast, depending on how many gaslog entries were made the previous day. Standard disclaimers would apply (EPA based, an approximation only, blah blah blah). If people don't like it chewing up CPU time (I don't think it would be a hog), it could have a turn off button.
Bad parts : More work for you. Some GasSavers might feel discouraged from entering their "below EPA" cars. The new EPA figures, however, will bring most people into "GasSaving" status, so I don't think that really matters.
I think it would be a good representation of GasSavers saving gas.