Both the narrow frame tankers and the frameless tank cars have 30 ton trucks, while a full load of crude may only be 45,000#, remember that the tank car body is quite heavy. When our team changed out 6 trucks on 3 frameless tank cars we were at maximum capacity of the forklift just lifting one end to pull the truck out. BTW I have heard the 6,000 number as well on the tank’s capacity.
When we replaced the decking, painted, and put all of the filling pipes and valves back on the Gramps oil racks in Chama, one of the things we found in the booth was a recording thermometer that would measure the temperature of the crude oil being pumped into the tank cars. Al Stevens took the thermometer home and restored it. As part of his research Al contacted the company who sold the thermometer to the Rio Grande and got a copy of the sales receipt!