I have a passing siding on my layout where a train pulls off the mainline, can stop at the station and continue on, or go into the inside loop, then on to the yards. Ole 2056 was derailing about every third time it went through the switches. I did everything to the switches you can imagine, no improvement. I just got a new F3 and was getting it ready to run, a little oil and lube, and it would soon be off. I decided to do the same to #2056 and as soon as I looked at the front trucks, I found my problem. The grime was horrible and I could not remember for sure the last time I had serviced the engine. A little (lot) of cleaning on the wheels, oil and lube and the engine runs a lot better than it did before. And no derailing through the switches!
What really struck me was the fact that the slow down in performance, though not great, was very apparent when the engine was properly lubed and oiled and running again. A regular system of maintenance is now in place on this part of the Milwaukee Road somewhere in Montana. By the time you notice that performance has fallen off because of not doing preventive maintenance, you are way past due.
Trains not running quite right??? Start with the basics; it works wonders!