Take a hypothetical car that uses 1/10th of your average one and then try leaving home with a pint glass worth of gasoline. You'ld probably won't even get to the gas station. If you watch Top Gear, go look up the old Geneve-Manchester single gas tank run those guys did. The guy that got the furthest was actually the gas-guzzling Jaguar that had a tank more than twice the size of others.
I don't need a car with a huge tank to save money, only a car that sucks less gasoline. Different points of view, i guess, i follow the orders of my healers :P
Actually, I'ld take the 20% more, because I can fill it up when the prices are lower(=non-stressful situations for healers) and save me more than that 1% efficiency will.
And you are right, it's much harder to suck less gasoline than to just add extra room for extra gasoline, but if you don't have enough money no matter how much gasoline you put at the beginning, it will suddenly end. So all you can do is to save that 1%, much better than being able to carry 20% more.
Goodnight now :)