Having just gone through all my old fuel reciepts, I decided to make a little web-based application to track and graph fuel economy for my vehicles. I've been recording the following on fill-ups (among other things):
- odometer reading
- time/date
- volume added to the tank.
The details are not that important other than to say that I have the data in a couple database tables and indexed, etc (for you computer geeks like me). I can sort it however I want. I'm trying to figure out a good general formula to give approximate mpg based on those numbers for generating datapoints on a graph.
I considered doing a simple "it took this much to fill up the tank and my last mileage readin was X" type thing, but then the thought occured to me that I don't ALWAYS fill up the tank, so it might be better to get my delta value over a couple fill-ups. It might not give me any more accurate individual results, but the curve, when plotted should be better over time.
So, what are y'all doing for your tracking? Spreadsheets? hand calculations, SQL with a web frontend like me?
Dan