The DL class provided the first diesel locomotive in service in Queensland, DL 1 being built to provide a light weight (maximum 6-long-ton or 6.1-tonne or 6.7-short-ton axle load) locomotive for the Mt Surprise – Forsayth section of the line from Mareeba, which since cyclonic rainfall in 1927 severely damaged the line, had only been able to support a rail motor hauling 1 or 2 goods wagons.

On their return to Mt Surprise they were shut down and hauled back to Cairns.When the upgrade to Forsayth was complete the 1720s went all the way and the DHs were no longer needed.

DL1 was retained by QR as part of its historical collection, while DL3 was preserved by the ARHS for use at the Rosewood Railway Museum.

[5] DL4 remains in service with Queensland Rail as a backup locomotive for the Gulflander on the Normanton to Croydon line.

[4] The DL class were mostly maintained at Cairns, but occasionally made trips to Ipswich Workshops for heavy overhaul, a practice that is still carried out by DL4 to this day.

Since then, it has performed essential shunting activities in Normanton and Croydon yards and has railed maintenance materials for the local track gang.

Some adjustments were made by the local Normanton crew on the suspension to correct some binding in the driver's side jackshaft crankpin.