There been many reports of AI cars running out of fuel (stopping in the middle of the track) in GTR-EVOLUTION/RaceOn/Race07 while using BTB/add-on tracks, after doing some searching around on the interweb, I managed to come across a format that seemingly works for fuel consumption.
Heres how to go about it:
1:In your created tracks directory locate the "yourtrackname.AIW" file, open it (I use Wordpad - because notepad didnt work for me)
2: Scroll down the file until you come across the "Waypoints" section, in that section you will find a "Tracklength" and "Fuel Usage" line.
3: using a calculator (unless your good at maths) take your "tracklength" and multiply it by 16.
4: take this total and place it in the "Fuel Usage" line BEFORE the decimal pont (apparently numbers after the point have no effect) eg: Fuel Usage=34567.00000.
5: I tried this on several occasions putting random numbers in that line and still had no positive outcome - the secret to this is to ensure you have the number in brackets. eg. Fuel Usage=(34567.00000)
6: Using this format the AI cars in my track now run for the entire race length and pit if required.
This format is untested in other games using the .AIW files but could work for them as well.
I hope this helps to sort out this "Fuel Usage" issue for other track builders as well.