I am not sure the exact gallons it holds, but probably somewhere around 3 - 4 gallons. It is mounted just behind the firewall on the right side, opposite the battery.
It is a good class and based on the two tracks we race on, one is 1/4 and the other 3/8, the Bando speeds are about 10 - 15 mph less than the Legends cars. Some tracks do have the Bandits and Outlaws divisions run different restrictor plate configurations, but our tracks here in FL don't do that. They race both divisions together un-restricted. I prefer that model of doing it because it is getting my 9 year old driver that much more experience racing with mostly 13 - 15 year olds and even a couple adults.
If you are looking for a class you can go the route of modified engines and such, you may want to look at the MiniCup class of cars. They are fully suspended and have front brakes as well. In addition most places have sealed engine platforms for beginners, but then also have unlimited classes for those that want to modify the engines.
My son currently races both a Bandolero and a MiniCup car and if he had to choose between the two, he would pick a MiniCup car all day long.