Originally Posted by southerlawn
A big thing to consider and remember is that FEDERAL LAW STATES ANY "TANK" DESINGED TO HOLD MORE THAN 115 GALLONS OF FUEL OF ANY KIND REQUIRES A HAZARDOUS MATERIALS ENDORSEMENT
You are talking DOT, not Federal Law.
Home heating oil tanks are routinely 225 gallons. So long as you don't fill them up with fuel and drive around with them, there is no issue, and the OP's question was about "on site" fuel. Not about a pony tank in his truck.
No, I have never heard of off-road gasoline. But you can still get the federal road taxes refunded at the end of the year. There is an IRS form for just that.
You just need to keep receipts that show the date, where you bought the fuel, and the number of gallons (price isn't important).
Just keep separate receipts for gasoline used for off-road purposes. Maybe get two gas cards. Use one for vehicles, and one for everything else?