Adds functionality and a locomotive for using fluids as fuel. Can use heavy oil, light oil, or diesel (if added by another mod), or all three. Configurable in Settings -> Mod Settings.
Sorry, its an oversight in my part. I will make a fix in a day or two, meanwhile, the only way I know is to delete all locomotive first then save again before uninstalling the mod.
If possible, please post it as a bug on main forum. Mainly because this save corruption bug is caused by rail_category bug in the base game, for more info see this thread, https://forums.factorio.com/viewtopic.php?f=23&t=49820 . Deletion of mod entities usually doesn't cause issues (except for rail apparently). I will make a manual workaround but it is a dirty trick that require unnecessary input from end user.