I have four of these, three purchased new. My standard procedure is to use CRC cleaner to completely degrease the trucks and lightly degrease the worm gear. I will adjust the wipers as needed. I basically run them dry. Pay special attention to where the contact on the truck rubs against the frame, as that gets dirty very easy and will kill performance because you will only have pick up from one truck. Expect warm grease to flow out of the upper body as they warm up, so you have repeat the process for every hour or so they run.
Kept clean, I have found them to be very good runners. If one pulls three cars, two will pull 8-9 cars and three will pull 15-20.
Bob