The tank cars operating on the Denver & Rio Grande did not belong to the railroad, but to oil companies such as the Continental Oil Company (Conoco) or to tank car companies such as the Union Tank Car Company (UTLX) or the General Transportation Company carrying oil for the Texas Company (Texaco). From the mid twenties to the mid sixties, the transport of petroleum products (crude and refined oil) was an important source of traffic for the Rio Grande. Crude oil was shipped from oilfields in the Farmington area to refineries in Utah via the Rio Grande Southern (RGS). The products of the Continental Oil Company refinery in Farmington were also sent to Utah, either via the RGS, or via Salida where the oil was transferred into standard gauge tank cars. The development of a large oilfield north of Chama required the building in the thirties of a pipeline to the railroad yard at Chama, from where the oil was then shipped in tank cars to the GRAMPS refinery in Alamosa. The oil from Chama was transported in UTLX tank cars, some of which were leased to the GRAMPS refinery and were bearing its markings. The GRAMPS refinery in Alamosa closed down in 1964, bringing an end to the transport of oil in tank cars on the Denver & Rio Grande Western narrow gauge.
The narrow gauge tank cars used on the Rio Grande were either old standard gauge tank cars whose tank were put on narrow gauge flat cars, or standard gauge tank cars converted to narrow gauge, often by the D&RGW shops in Alamosa, by rebuilding their frame or simply exchanging their trucks. The UTLX tank cars were old standard gauge cars dating from 1908 and 1912, were equipped with Van Dyke tanks (the tanks were lying directly on the trucks with only saddles to support them) and had kept their original numbers. They were converted into two classes of narrow gauge cars, narrow frame tank cars, and frameless tank cars. The UTLX narrow frame tank cars (named by contrast to the Conoco tank cars, equipped with larger frames) were the oldest, about thirty had been converted to narrow gauge between 1924 and 1930. They rode on archbar trucks and most of them were equipped with heaters, their original numbers were in the 12000 to 13999 block. In 1947 they have been renumbered in the 88000 block and again in 1956 from 11000 to 11033. In 1956, two of these tank cars were transfered to the D&RGW, to be used as auxiliary water tanks for rotary snowplows OM and OY. In 1962-63, the UTLX got rid of its narrow frame tank cars, 16 were sold to the White Pass & Yukon (WP&YR) in Alaska, where they became WP&YR tank cars #50 to 65. Eight of these tank cars recently returned to Colorado, six are now preserved on the Cumbres & Toltec Scenic Railroad, and two at the Colorado Railroad Museum. Another former WP&YR tank car, #61, is today on the Sumpter Valley in Oregon.
About thirty frameless tank cars were built for the UTLX from Van Dyke tanks put on new narrow gauge Andrews trucks made by American Steel Foundries. Most of these conversions dated from the early thirties, a few other were done later until 1947. These tank cars were also equipped with standard gauge trucks that could be exchanged with their narrow gauge trucks whenever needed. In 1939, 25 of these frameless tank cars received new Bettendorf trucks, still built by American Steel Foundries, with journal boxes cast in the truck frames. In addition to these tank cars used regularly on the D&RGW, several other cars have been temporarily converted to narrow gauge from standard gauge frameless tank cars when the amount of traffic required it. The UTLX frameless tank cars were originally numbered in the 55000 to 55999 and 57400 to 59999 blocks. In 1947 they have been renumbered 88150 and higher, according to the type of their heater. And those not already scrapped were renumbered again in 1956 from 11034 to 11058. Just before 1940, most frameless tank cars have been labelled GRAMPS, the nickname of the owner of a refinery in Alamosa, with large letters on their tanks. These cars were all retired in 1965, at least four are preserved today, including one at the Colorado Railroad Museum, another on the Georgetown Loop Railroad and a third with GRAMPS letterings in Central City.
UTLX narrow frame tank car #88125, it carried this number between the renumberings of 1947 and 1956 (formerly #12770). It is currently preserved at the Colorado Railroad Museum.
Frameless tank car GLFT 1 at the Georgetown Loop Railroad. It is probably former UTLX frameless tank car #55328.
UTLX frameless tank car #11058, preserved at the Colorado Railroad Museum in Golden.
B end of narrow frame tank car #12770, this time carrying its original number.
In Chama on the Cumbres & Toltec Scenic Railroad, UTLX narrow frame tank car #12739.
UTLX frameless tank car #11058, seen from its B end during a switching move at the Colorado Railroad Museum.
UTLX narrow frame tank car #12962 in Chama, one of six of this type preserved in working order on the Cumbres & Toltec Scenic Railroad.
WP&YR tank car #53 in Skagway, Alaska. Its tank comes from former UTLX narrow frame tank car #12838, bought in 1962 by the WP&YR.