Is OTHER wrong in the post ? POST : This is something that happens often with one friend and I'm worried that I'm being a major prick.

We're both 18 and like to hang out a lot, we've been practically glued to each other since middle school. He's usually the one who drives because he insists on it. He drives a frankly badass Porsche from the 80's that he bought front a junk yard broken for cheap, then fixed it up over a couple years. Problem is that it eats gas like your 300lbs uncle during Thanksgiving, and we generally always have to get gas. 

He has a job and never spends money. He literally holds at least 500 on him at any given time, but he always asks for money when he gets gas. I gave him money once or twice because he is the one who always drives, but lately I've been denying him. I'll just say "C'mon man!" whenever he asks and he'll just say something like "Alright, alright..." then pay himself. I'm not trying to be a dick about it but it feels like he should be the one to pay. Am I the asshole?