It's wrong to screw up his business with a demonstration, mini or otherwise, and you're going to have confrontations with people who just want to gas up and get to work, not read some leaflet.
The original OWS (accept no substitutes) correctly targeted the group responsible for the economic outrages being perpetrated upon the citizens of this country. Nothing has changed and nothing will until the system that allows these ripoffs is allowed (some would say 'encouraged') to continue. You're right - there is what amounts to an oligarchy manipulating gas prices and pretty much everything else in the economy for their own benefit, but I seriously doubt if showing up a a gas station in a fawkes mask is going to change things very much.
Here's a link you might find interesting.
http://abcnews.go.com/blogs/business/2012/02/how-wall-st-is-raising-the-price-of-gas/
Some excerpts:
"What may surprise you, however, is what one of Wall Street’s top regulators has to say about who else you’re paying: speculators on Wall Street.
Bart Chilton, a commissioner at the Commodity Futures Trading Commission, the federal agency that regulates commodity futures and option trading in the United States, said it’s time to look at home — in addition to overseas — when searching for the reasons why gas prices are on the rise
<snip>
By Chilton’s calculation, if you drive a car like a Honda Civic, you’re paying $7.30 more than you should every time you fill up — to Wall Street speculators. If your car is a Ford Explorer you’re paying an extra $10.41.
For a Ford F150, he says owners pay an additional $14.56 per fill up -or more than $750 a year.