Lots of assumptions here !
Take a train of 50 off 23,000 US gallon tankers.
Total fuel weight would be 4,200 tons and therefore total loco fuel used for the 478 mile journey = 4200 gallons.
4200 divided by 478 = 8.78 US gallons per mile.
(if my maths is correct)
Don't know if one loco could haul 4,200 tons though !!
Pro rata a 25 wagon train would do 4.39 US gallons per mile.