Gas prices in Milwaukee average $3.17/gallon right now. Even with a 20 gallon tank in your car (and it's probably 12 or 15 gallons), if you timed it perfectly, so that your tank was empty, you'd be getting onyl $63.40 worth of free gas. If, more likely, you got 10 gallons of gas, that's $31.70.
If I announced that I was doing the same thing, but instead of giving out gas, was going to give $50 to each car that came, do you think there would be more, fewer, or the same number of people willing to wait more than 6 hours overnight (and sleep in their car)? I think there'd be fewer. To make the exercise easier, suppose I gave out the exact amount of money needed to fill your tank at a gas station just around the corner from me. More, fewer, or the same number of takers? Remember, this is more valuable, because you can use the money on anything, not just gas. (Although gas consumption is probably inelastic enough that this difference is negligable.) Still, I'm betting there would be far fewer people. (Unless I pitched it as a "free gas" giveaway....)