I think that would make the game even better.
It really would depend on how they implemented it. If it was like the whole "hunger" thing in GTA:SA, that would suck and just be an annoyance. If it was realistic and you could drive around for a good amount of time, it would be kinda cool.
Either way, I highly, HIGHLY doubt they'd do that. They already announced that they wouldn't be bringing back weightlifting, hunger or anything like that because it takes away from the overall experience of the game. Also, when you factor in things like different cars having different MPGs, cars being parked on the street with less than a full tank, driving style (running out of gas faster if you're flooring it than if you're driving casually), it would take up a lot of disc space and effort on the developer's part for a completely useless feature. The game is already pegged to be bigger than Liberty City and San Andreas combined, I doubt they have much space left for such frivolous things lol.
