How to properly calculate numbers when switching fuel type?

[swarbrz]

Originally Posted by litesong

I just start a "new car" in my garage in fuelly, using E10 in one "car" & E0(100% ethanol-free gasoline) in another "car" in fuelly.

I don't think you understand the problem.
Car has e10 gas, I fill up with e85. The data fields for my fill up are for e85 as I just filled it. BUT I was just driving with e10 so my mileage was for e10.

Problem will occur every time I switch fuel, thus making all of my average data inaccurate.

Also a problem with people who fill with different brands or octane ratings, if you fill brand A today and enter the mileage, the previous fill was Brand B, thus making your calculations of brand/octane off by one fill up. I personally average 2 mpg different between certain brands, making the cheaper brand more expensive per mile!

This is making me not enjoy the experience as I now know that the data is only accurate if you fill at the same place and fuel every time. That may work for average person. But for people like me who joined for the accuracy, it isn't accurate...

I will try to stick to e85 as long as possible, but when I can't find it, I will be forced to go back to e10 and thus reminding me that fuelly is not accurate and make me not want to use it anymore.