How would you get gas money from your friends?

Just bring up the fact that gas is so expensive these days that you sometimes avoid driving. See if they get the hint that they should help you pay for what they did. If they dont say "listen here biznatches, I took me time to drive you to that ******* thing at lookee her what time. Youze be best taking out some dam money to pay 4 dat gasoline i use for you or you be getting some dam trouble. Be sure to be as loud and obnoxious as possible when doing so" they'll get the picture