Garden City Jeep
Don't blame the dealer. A salesman? Will tell you it gets 150mpg and does 0 to 60 in 3.0 flat to sell you something. There are lots of places to research that..it's part of car shopping, not listening to salesmen. Or women of course. That is the least reliable source, as you discovered the hard way.
That's the third dealer you have posted that. He advertised 13 mpg and you get 12..? If you are all that concerned about mileage don't buy a gas sucking 4000lb tank
Gas mileage is usually listed on pricing websites like NADA, Kelley Blue Book, Consumer Reports, etc. BUT these are A.) Estimates and B.) When the vehicle was new. Depends on your driving habits as well. My Father got 18 MPG when he drove my, then new, '86 Chevy C-10 pick up. I got 10 MPG tops when I drove it. But I was 20 years old then and still indestructible. HTH. -Jim