This is the sort of thing that keeps me up at night.

[HUnewearl_Meira]

This is very, very rough, but I think it's rather revealing.

The conditions assume that the vehicle is traveling on a perfectly flat surface, and the engine performs with 100% efficiency. The gasoline taken into consideration is US Regular Unleaded.

We will now work out, the maximum possible MPG rating of a standard, gasoline-only vehicle.

Mass of a car: 990kg ~ 2000kg (Cars vary in mass-- this is an approximation)
Travel 1 mile = 1,609.344 joules per kg (We assume that the car has accelerated to its optimal speed before measurement begins, and all energy being added goes strictly to balancing against drag)
Travel 1 mile in a car = 1,593,250.56 joules ~ 3,218,688 joules (Mass of Car * joules per kg)

1 Gallon of Gasoline = 120,381,873 joules

Therefore--

Maximum possible distance traveled with 1 gallon:
120,381,873 / (1,593,250.56 | 3,218,688)
75.55740197 miles ~ 37.40091397 miles

Based on this information, we can suppose that any advertisement stating that a vehicle gets in excess of 75.5 MPG must be either for a hybrid, or lying. Vehicles on the larger end of the scale are unlikely to exceed 40 MPG, getting around 37 MPG at most.

And now you know.

If there is some important consideration that I've missed, feel free to point it out-- just be aware that this assumes that the gasoline is used to its maximum potential, and that any mileage rating will necessarily be lower.

[ShinMaruku]

If you use diesel you can get an excess of about 400 miles on one tank. Well somtimes.
But things are rarely optimal.

[HUnewearl_Meira]

Well, my Yaris gets in excess of 400 miles out of one tank, as well. It gets about 40 MPG on the highway. I believe that car manufacturers choose the size of the gas tank based on a goal of getting between 300 and 450 miles.

[ShinMaruku]

Lucky California is hard assing some manufacturers to have a bit higher milage as that pushes some to even more exelence in design. I like how VW does their Mileage although they also have the worst mileage (Bugatti Veyron at 455km/h)

[HAYABUSA-FMW-]

If there is some important consideration that I've missed, feel free to point it out-- just be aware that this assumes that the gasoline is used to its maximum potential, and that any mileage rating will necessarily be lower.

Saw $4.41 /gal today on fats food row.

Governator's underground supply to run his killbots, bought in advance of the purge, in order to purge. Witches be damned.

[Palle]

Saw $4.41 /gal today on fats food row.

Governator's underground supply to run his killbots, bought in advance of the purge, in order to purge. Witches be damned.

No better in the Yay Area.

When I drove my car it went about 280 miles to a tank, but I'm not the smartest driver [e.g. 80mph]. Now it's covered in leaves and a fine coating of pollen.

Wallet rejoices.