It not free. They cap gas at $2.99/gal and anything over that, per gal, they pay. Also, the 12,000 miles a year will not be based on mileage but typical gas mileage for your vehicle. So, if you use up too much gas having fun or driving city, you get screwed on the deal.
Too many restrictions and unknowns: sounds like a good way to piss off customers.
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'13 Mustang 3.7V6 - MT82
'00 GP SE (L67 Swap, XP, Headers, 3.25")
'98 GTP, '01 Bonne