Hm you could read the scheme description I gave with the scheme.
You have unlimited jetpacks, and unlimited time, and unlimited nades, but the rule is to use only one jetpack each turn, so you fly away your fuel and use some retreat time after dropping the nade. This is not as boring as the other scheme. The one who can use his fuel better gets further, simple.
Edit:
Ok this is no pure fuel trial, but it teaches both skills, flying fast, and flying with as less fuel as possible. If both players get to the finish in their retreat time, you just fly back the map when you reach finish, to see, who gets further.