We have had several of our Customers have us look into problems suffered on Mechanical Lubricators and associated problems on their Locomotives. Some of the major problems encountered was that the Oil used was in the range of 600 Weight Gear Oil not Steam Cylinder Oil for a start. This was also being done at ambient which added to a Problem dealing mainly in priming of the Mechanical Pumps. From Full Size Locomotives to Backyard Railroads we have seen this problem over and over. Most Manufacturers of Mechanical Oilers recommended heating the oil reservoir to about 120 Degrees Fahrenheit.The Railway Lubrication Manual by Imperial Oil Limited also recommends never exceeding 150 Degrees Fahrenheit due to the effect on the animal constituents being affected at atmospheric temperature along with the paraffin additive. In most cases we recommended a steam trace line just run under the Mechanical Lubricator. Most of the Big Railroads did this and added a choke so as not to over heat the reservoir. The other recommendation to solve this problem was to use a lighter cylinder oil with the proper paraffin and tallow additives blended properly. This has stopped our customers' piston rods from bluing from the heat and that awful squeak or moan that accompanies this. We hope this helps you once you get out of the steaming bay.
Whistles & Bells!