Athearn HO Guage Southern Pacific Fuel Tankers

A pair of fuel tankers here. They look like oil cars but are slightly different. The silver car is for Deisel fuel and the mustard color car is gasoline. As chemical cars were owned by the chemical companies and these are marked Southern Pacific they had to be for use by the railroad. The locomotives run on diesel and one supposes they had a use for gasoline. Makes sense they wouldn't pay someone else to carry their fuel.
The two cars have different couplers. The mustard colored car has the old style couplers, which are easy to work with hooking up and HO train. The silver car has the newer couplers that are more realistic. I believe they are called Kaydee style or some such.
The train is being pulled by a GP 38-2.