Upon reading the title of this article one may rightfully wonder why lubricating the cylinders of our restored hobby engines is any different than it ever was.
The one great difference is in the operating temperature of the cylinders. The pressure on the aging boilers has been reduced. Many of our engines are seldom, if ever, pulled as they once were. In either case the result is the same: there simply isn't enough heat to emulsify the oil. The cylinders are working 'wetter' which helps to flush away the lubrication that does exist. Since water is somewhat of a lubricant and the engines are seldom worked, the poor lubrication most of these engines are getting is simply not noticed. Some look for milky water emitting from the cocks and glands. This is about like the ground hog and his shadow, it may or may not be an indicator of sufficient lubrication.
The lubricant of most farm engines before 1890 was tallow. It was a good emulsifier and had satisfactory film strength up to about 125 lbs. of pressure. As pressures began to exceed this mineral oil with a 2 or 3% addition of tallow came into use and was referred to as 'low pressure steam cylinder oil.' The mineral oil was of a dark, straight stock and of a viscosity of about 160 SSU. Heavier bodied mineral oils without tallow were generally used at about 200 lbs. pressure of working pressure. These are not suitable for our engines.
The writer has never run across any commercially available low pressure steam cylinder oil with over 3% tallow. This oil does not have enough tallow for our conditions.
An excellent oil can be compounded by taking four gallons of either low pressure cylinder oil or a straight dark stock 160 SSU oil. Add one gallon of acid less tallow. Tallow can be obtained by getting the suet from a butcher shop. This suet lies in the back of the animal and is practically pure tallow. Any red meat must be trimmed off as this will produce acid which will destroy the tallow in time. The writer recently opened a gallon of tallow that was in excellent condition after 13 years. The suet can be rendered in an oven at about 250°F. Your wife's oven will do fine if she is not home!
While the tallow is hot, strain it through a couple of layers of cheesecloth or tobacco cloth directly into the oil which should at least be warm. Next add about a pint of bubble soap that you can get at nearly any dime store. At times they have this in pint economy sizes which are much cheaper than the small bottles. Shake this mixture while still hot. It will settle very little, even over a long period of time. The viscosity increase will not be objectionable during the summer months even when poured at ambient temperature.
The bubble soap is an excellent emulsifier. When your packing glands are correctly adjusted clusters of oil bubbles will hang from them. You will find that your engine will roll easier and the valve gear will be quieter. The writer has used this 'homemade' cylinder oil for the past 17 years and has never had any problems with it.
One more comment: induce the oil into the center of the steam column. A small copper tube brazed or soldered into the steam line fitting to carry the oil to the center will do the trick.