"Guys, wait! Look out for the barrier!"
The Diesel Headquarters is a location in Quest 89.
The Diesel Headquarters first appeared in Connor V.S. Diesel, where it was seen as some sort of run down shed with broken machinery and pieces of scrap. One was a blue truck that was eventually modified into the Road-Rail Transporter. There is an oil derrick there as well, but is isn't seen being used. There is a small turntable infront of the sheds, to small for engines like D199 and Connor to use, implying it was made for the smaller troops of The Diesel Army. Although not the best fortress, it surved it's purpose all the way up until the point where Connor seized control of it. The latter and Charlie had a machine constructed from the scrap and machines to make a lorry that would transport engines on road, but that's another story.
- It is unknown what happened to the fortress after the ninth episode, Connor could have had it destroyed, or he could have just left it.