On entering my latest stats onto Fuelly, it returned my best yet mpg of 108 mpg. Sadly that is some 30% better than in reality and for the life of me I can't understand why that should be. The Prius has shown a consistent monthly average of between 60 and 70 mpg on it stats page, so assuming there's an error, (either mine or the app's) I've elected to remove the Fuelly badge from my posts and discontinue its use.
How are you entering data? In my case I enter the odometer reading (let Fuelly do the math, subtract my previous odo entry) and the gas volume. Is there also an option to enter distance? I'm thinking you've mis-entered one of those two values, somehow? Are you doing a spreadsheet too?
No spreadsheet, but I've entered data like you said and been reasonably satisfied until now. I rechecked my figures several times and even fudged the previous mileage in case there was a 200 mile error there, but it's still way too high. Now I know the car is near enough accurate for my purposes, there is no need for me to update Fuelly with potentially flawed data. That will only skew the figures for bigger Prius picture. Hope everyone understands.
I'm not blaming Fuelly as it's possibly my error causing this blip, but I have no wish to keep the records now.
I added a dummy fillup (it's all I got), purposely tuned to return 5.0 liters per 100 km. It seem to go in ok, and my average didn't jump/change. I did notice the add a fillup page looked very odd, bare bones appearance, like it's under maintenance?
Mine is within one decimal point of my spreadsheet. It could be that the pump/bowser cut off before it was really full. I had that one time, a bit surprised when it didn't take as much as I expected, then driving away the gauge only showed a little over half. I went back and tried again and it took 12 more litres.
I am flummoxed. You provided Fuelly with the last two odometer readings and how much gas you put in. It does one subtraction operation, and one division operation. Fuelly could not have screwed that up. The "only" way it will give bad results like you saw is if you didn't fill up your tank all the way the last time -- or if you gave Fuelly the wrong mileage or fuel amount. Or -- and this is my working theory -- you have a kid, wife or girlfriend who borrowed your car when you were sleeping, and one of them (or each of them?) put some gas in the tank in the hope you would be none the wiser.
Sorry to say that none of the above apply in this case. It only went wrong once before when I failed to note the odo on a fillup away from home and after the next one averaged out OK. As far as I'm concerned I've learned enough from 13 fills that I average between 60-70 mog folk mixed driving. My Fuelly app is no more.
One of the reasons I keep my spreadsheet going on each car (starting in 1990) - and now FUELLY is to track when something is going wrong. My spreadsheet can produce a graph - if it took a gradual dip I'd change plugs and points, timing, brakes for binding, check valve clearances etc etc. OK, on Prius, most of that isn't applicable, but it would show trends like if I changed tyres etc.
I joined Prius after several years of just tracking with a spreadsheet. In that process I learned there is a way to import a spreadsheet, it just needs to have the data in a specific format, which I did. This is the format:
IIRC they have heuristics in place to yank out any heavy outliers. I wouldn't worry about Fuelly; I would be worried that either you have a paranoid fuel fill cutoff or the world's most efficient Prius.
The only times I get extremely great mileage in Fuelly is when I neglected to enter a fill-up. It's happened more than once...
