I kinda like the bar or line-graph idea, per each vehicle in the garage. Also, I agree with the City/Hwy entry and to keep the comments field. Just brainstorming, but a weather conditions field might help too.
one more idea: would be good to be able to incorporate the EPA/NRCan ratings for each vehicle to be able to view each driver's hypermileage status (the statement refers to exceeding the ratings, doesn't it dan?)
My understanding of hypermileage is when someone exceeds the combined EPA ratings for thier vehicle. This was the terminology on the other website. You had to have at least 3 tanks to qualify. Hyper=over achieve to some standard. So for my Prius, rated at 60/51/55 combined, one would have to maintain at least 55MPG average after three tanks to qualify. For the del Sol, 34/38, i would need 36MPG to qualify.
A further variation on the theme is "valedictorian hypermiler". To qualify, you had to beat the combined by 15 0r 20%, I can't remember exactly. Wayne Gerdes who coined the terminology and maintained the hypermiler thread at GH may possibly be starting his own website shortly. Like gas savers, it would not focus on hybrids, rather on all cars. IMO, Diesel owners did not feel welcome at GH because of the large population of environmentalists there.
I added my tanks to the gaslog today. Sorry MetroMPG for knocking you off of the top spot. :-(
Guess I am heading for hypermiler real soon since the xB is rated 30/33 and I am in the low 40's.
The Brand of gas should be for the fillup as well as the price otherwise you could get confused - the current fillup will show what the prior gas type has given - no other way would be clear to use. I don't know what I started with when the dealer filled it up anyway. Simple to have the columns for the common additives and then a couple for fill in.