BTW...this is much your fault as anyone else's.
Fuel cost should be divied up by all participants. That's sorta the unspoken rule, isn't it? That's how we've always done it (except when I've taken dates out - see KC's post).
The day starts out: "OK guys.....fuel cost came to $90......so that's $30 a piece."
Do it this way and everyone feels they are more a part of the excursion than just some "dead weight" along for the ride.
You're actually doing them a a favor.
Makes sure they pay in cash, too!