Re: Then you must have seen this picture.

These cars would have been used to move refined products from a refinery (or standard guage transload) to a bulk plant. My guess is there were bulk plants for various oil companies at about every major town on the the ng. So part of the answer as to where they were used would be where were there refineries or transloads. Obviously there was as least one refinery at Antonito. Were there any other refineries on the ng? Transloads? I might also mention the oil companies tended to trade product when it was convenient. So a Texaco bulk distributor would not necessarily get his product from a Texaco refinery.