Which parts of a model railway locomotive do I need to oil?

Knowing which parts of your model railway locomotive to oil can be a little mystifying, especially if you no longer have the servicing guide supplied when the model was new. So here are a few tips that may help.

The first thing to consider is whether your locomotive needs oiling in the first place. Preventative oiling can often cause more problems than it solves, especially as we tend to forget about scale and swamp our poor little locos with a scale gallon or two of the gloopy stuff. So keep oiling to a minimum, and when you do, use oil extremely sparingly. But when the time does come for a little TLC, the main parts that will require oiling are as follows:

Inside your model, the motor will connect to the wheels through a combination of cogs, worm gears and driveshafts. It is unlikely your model will have all of these, but it will have at least one, and as they produce friction, these require lubricating (usually after a model has been sat in storage for a prolonged period). Again, it cannot be stressed enough that only the smallest amount of oil is needed. Try using the end of an unfolded paperclip to collect just one drop of oil, that is the kind of minimal quantity required.
Once you have your microscopic drop of oil, it can be carefully placed onto the teeth of a cog or screw or the knuckle joints of a driveshaft and it will naturally work its way around the mechanism as the loco runs.
While you are poking around inside your loco, never be tempted to try and oil the motor itself, it won't like it and probably will never run right again. If your motor is squealing a little, use just a dab of oil at the point where the primary shaft leaves the motor, but never inside it.
Back on the outside of your loco, a spot of oil can be used on the joints of a steam locomotive's valve gear assembly and on all locomotives where the wheel axles disappear into the chassis, but again, less is more when it comes to oiling.

Avoid oiling the centres of spoked steam engine wheels where the axle pokes through the wheel. Often model wheels are a complicated combination of insulating plastic parts attached to conducting metal ones, and oil can only mess things up in that department, so as there are no friction-reducing benefits to oiling wheels in this place, it is not required.

Oiling a model railway locomotive can help it run smoothly, but over oiling it can completely ruin it, so be very careful when attempting it yourself. Many servicing guides are available online to help you, and even if you can't find your exact model, it will give you a good idea of what to, and more importantly, what not to oil.