Three reasons we are not winning, and we are working on them.
1) Mechanical issues: We have never grenaded, but one race the exhaust system broke and we were flagged for sound. Any time off track to fix a mechanical pretty much puts you out of the running. We were down for probably 1 hr or more on just that. Another race we had the fuel vent plug combined with the exhaust boiling the gas out of the filler - probably 2-3 hours troubleshooting and repairs over about 3 different black flags when it did not work. Last race we lost about 30 minutes due to a defective **** switch. Not the end of the world, but winning is all about track time.
2) Driver changes: We started the races with the goal of having fun. To do that, we made sure drivers all got pretty equal time both day and night. We were changing drivers every hour or so to get everybody throught the rotation in case we broke. Now we are more seasoned and know that each driver change is 10 minutes minimum, more if you take on fuel. It adds up quick. Lately, we have been running drivers until they are out of fuel or out of energy. It makes a world of difference.
3) Penalties: Our team is a recovering penalty magnet. Our first race had probably 3 -4 hours of combined penalty time. Passing under yellow is a really easy thing to do in the heat of the moment. The Halloween race we only had one penalty, and it was supposed to go to another team, but we got dinged with it (two hours). Last race we drove clean; we were the only team to not get any penalties. Coincidentally, we had our highest percentage finish at the last race. We kept climbing in the ranking, and then we would pull a driver change. Some of the teams were going over 3 hours between changes, when we were going 2. It adds up over 24 hours.
As for winning, We held first place after 3 hours at the Halloween race - right up to the 2 hour penalty for hitting a barrier we did not hit. Had we not had that penalty, I think we would have finished top 5. The car can do it. The team can do it. It is just a matter of getting everything together at the same time.
That said, the original question of fuel tank size stands. Put the biggest tank in they will let you have and run it as long as you can between changes.
Mike