Auxiliary Fuel Cars

A Unity Mod Manager mod for Railroader that adds auxiliary tender and fuel cars to extend the range of steam and diesel locomotives.

Cars spawn with 20% fuel by default (configurable in the UMM settings panel). Aux cars drain first then the locomotive's primary supply only starts dropping once the aux is empty.

Cars

Steam Aux Tender (AUXT)

Reuses the K5 Pacific (P-43) tender model. Carries both coal and water, matching vanilla P-43 tender capacity. Couple it behind the primary tender, and coal and water are topped up automatically every fuel tick.

Name	Coal	Water
Aux Tender	30,000 lb	10,000 gal

Standard consist: [Steam Loco] — [Primary Tender] — [Aux Tender]

Back-to-back MU: A single shared aux tender between two locos is supported.
[Loco 1] — [Tender 1] — [Aux Tender] — [Tender 2] — [Loco 2]

Can be filled at coal loaders and water towers normally.

Diesel Fuel Tender (DT)

Reuses the USRA single-dome tank car (tankcar02) model. Couple it at either end of a diesel locomotive — diesel fuel is topped up automatically each fuel tick. Can be filled at fuel stands and accepts interchange waybills.

Name	Diesel
Diesel Fuel Tender	8,000 gal

Consist: [Aux Tank] — [Diesel Loco] or [Diesel Loco] — [Aux Tank]

Cost

Aux Tender (AUXT): $4,000

Diesel Fuel Tender (DT): $1,200

Settings

Accessible from the UMM mod menu in-game.

Setting	Default	Description
Fuel loading speed multiplier	10×	Speeds up filling at service points
Starting fuel on placement	20%	How full aux cars spawn

MU Safety

• Only cars with carType DT or AUXT are eligible as aux sources; vanilla rolling stock and third-party cars are never touched.
• A patch to BaseLocomotive.FindSourceLocomotive ensures MU control passes through aux cars transparently in a consist.

Installation

1. Install Unity Mod Manager for Railroader if you haven't already.
2. Download the latest release zip and install it via the UMM installer, or extract the AuxiliaryFuelCars folder into your Mods directory.
3. Launch the game and the new cars appear in the car placer immediately. Vanilla model bundles are copied from your game files on first run.

Compatibility

• Railloader: not required and not used.
• DPC / DPU mods: no conflict — fuel transfer is fully independent of MU control.

Bugs

Report bugs at GitHub