So, ah… it’s kind of true, yes, but not the way he’s doing it. He’s filling it when it drops to half, so he’s carrying a full load all the time, which is more weight. If he waited until it was near empty and then put $20 in, your point would be correct, although the savings is so small - (3 to 5 cents per gallon per 100 pounds of weight saved; a big SUV might have a 30 to 40 gallon tank, gas is roughly six pounds per gallon, so 120 is about the most weight he’d save at half full) - that it’s not really going to be that big a difference. And he’s driving a giant, gas-guzzling SUV, not a hatchback.
i kinda like going to the gas station. even better when i fill my truck and my boat in the same trip!
those little tv’s in the pump showing the same five-second clip from last night’s nba game, the windshield wash and squeegee, the petrol fumes! good times, man. good times.
eta: that’s a USD$300 bill right there, between the two. and it does make sense to keep the boat’s tank full of rec90 petrol so it doesn’t allow rubber seals to break down and draw in water from the humid south florida air.
a big YMMV is noted here.
Stopping and starting the engine for the fill up would immediately cancel out those weight savings and possibly more.
Not to mention that he somehow thinks, and repeats over and over again, that $20 fills his $80 tank from half full to full. This is only true, as others pointed out above, unless his fuel gauge is really inaccurate.