HUnewearl_Meira
May 5, 2011, 03:47 AM
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.
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.