How many gallons of gas does a train hold? An SD40–2 locomotive - a 3,000 HP standard line-haul workhouse of the past used by most North American RR holds 3,200 to 4,000 gallons of fuel. A typical switching locomotice - EMD MP 1500 - a 1,500 HP standard switching locomotive will hold 1,100 to 14,00 gallons of fuel.