Well I set a new record on miles per tank and gallons per fillup. The last tank was 14.3 gallon fillup and went 573 miles on 93 octane. The previous best was 13.7 gallon fillup and went 500 miles on 87 octane. Well now with 14.4 gallon fillup with 93 octane we will see how far I can go. The switch to 92-93 octane is to see if the higher alcohol content in 87 octane is affecting my mpg's vs the much lower to 0% alcohol content in 92-93. The last 8 tankfuls with 87 avg'd 36.75mpg, this last tank avg'd 39.75 mpg's so far. More tanks of 92-93 to test to get a good average. So will it be cost effective to use 92-93 vs 87 as a $/mile aspect? With the 3mpg and $.30/gallon difference it is a wash so far, you go further per tank but the overall cost is the same.
Till the next fillup in 500 plus hopefully 600 miles from now...........

It seems to me like it wouldn't be terribly safe to pack all that fuel in something that isn't meant to hold that much. If the gas tank gets too hot wouldn't the fuel have to expand somewhere?

But if you want to do it, then why not.

In 1946, stunt pilot Paul Mantz won the coast to coast Bendix Trophy race in a P-51 in which he loaded cooled fuel. He had dry ice loaded into the fuel truck the night before the race. So if you really want to go crazy....

Alternatively, back around 1979, we made a trip down to Florida in a small camper converted van towing a boat. We had two 30 gallon barrels of gas in the boat. There was a tube going from the barrels to the filler pipe on the camper (sealed with duct tape) with a 12v electric pump wired to a cigarette lighter plug. When the gas gauge got down to 1/4 tank we plugged the pump in and filled the tank to 3/4 tank. The van had a potty on board, so the only other challenge was to swap drivers on the fly. Aaahhhh.....the good old days. It's a wonder we survived them.

yea the gas can expand and start going into the evap system, wreaking all sorts of fun havoc.

TDIs have what they call a vent that keeps a gallon or two out of the tank. The release the vent and fill up. It's called venting, and some go as far as a ventectomy and remove it. Just remember to drive the gallon or two down so it doesn't expand and cause problems.