ok, I think I found a way to address this going forward. From now on you can change the order of fuel-ups on the graph by giving fuel-ups on the same day a different fuel-up time. Normally when you add two fuel-ups on the same day the time is recorded as exactly the same. (Or, more precisely, the time isn't considered important.) If you go in and edit a fuel-up you have the option to set a time as well. If you set a later time for one of your same day fuel-ups, it will appear in the correct order on the graph.
I went ahead and set the time of your 2nd fuel-up on Oct 23rd '12:00 PM'. (You can change to to the correct time if you recorded it/remember it.) That should make your graph line up the way you want it too. It's an extra step for same-day fuel-ups but it will help make everything more accurate if you want to do it.
Thanks for the fix though. At least its a way to prevent issues. Though, it might be simpler to just stamp it with the time its entered for both fuelup_date and date_added. At least that will prevent issues with the less understanding members?
In other words, the time you enter the fill up would be used for both, regardless if the dates were the same day or if you actually had to go pick the day the fill up was done, it would be stamped that time. Cause there would really be no way to enter two entries AT the same time, and this would prevent the issue. And those that are more fussy can go edit the actual entry and still adjust the time if they feel its necessary.
People enter fuel-ups out of order all the time. They often start with the most recent and work their way back through their receipts. The entry date really shouldn't be used for any sort of sorting. I don't think that wouldn't solve it.
I know it's a slight hassle, but I think including the time will fix this.