How can a train haul 1 ton of freight 500 miles on 1 gallon of diesel?

There is a commercial on TV by a local railroad that claims to be able to move 1 ton of freight 500 miles on 1 gallon of diesel. I realize that they are looking at that one ton of freight as a portion of the entire load of the train and how much fuel it takes to move the whole train 500 miles, but does anyone know... show more There is a commercial on TV by a local railroad that claims to be able to move 1 ton of freight 500 miles on 1 gallon of diesel. I realize that they are looking at that one ton of freight as a portion of the entire load of the train and how much fuel it takes to move the whole train 500 miles, but does anyone know what the math was?
How many cars on a typical train?
What is the weight load of a typical car?
What is the mileage (miles per gallon) of a locomotive?
What is the fuel capacity and range of a locomotive?

I am trying to recreate the math that was used to make this claim.
Update: Thanks for all the helpful info folks. I'll leave the question open so that others may chime in.

Oh and BTW, I saw the commercial again. It is CSX making the claim.
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