Lubricating-oil, despite the abuse it receives, is expected to perform its function properly. Road dust, gasoline and water are allowed to mix with it, and it is subjected to a high temperature and mixed with carbon, so that the original oil soon becomes hardly recognizable. Some remedies that have been proposed provide for the removal of either the dirt or the dilution, but both should be kept out. Water not only dilutes the oil, but forms sulphurous acid, rusting the parts and, in winter, probably freezing at the oil-pump. When mixed with oil, it forms an emulsion and when this emulsion is mixed with road dust or carbon particles, sludge is gradually formed. Sludge, when agitated and sucked through the oil-pump, tends to clog the oil-holes and to wear the bearings. Oil, when exposed to a high temperature on the cylinder-walls, becomes oxidized and black in color. Sulphur in the fuel probably forms sulphur dioxide and, by mixing with water in the crankcase, becomes sulphurous acid.
A rectifier is described that has been designed to take out all the water and to keep the diluent between 4 and 5 per cent and the viscosity above 250 sec. at 100 deg. fahr., the oil being forced through by pressure of the oil-pump at the rate of about 3 gal. per hr., that of an ordinary crankcase being filtered and going through the distilling apparatus about once every hour. Emphasis is placed on the fact that, in accordance with Dalton's law, gasoline can be removed from oil without heating it to a high temperature; that practically all the gasoline diluent can be removed at a somewhat lower temperature than would be supposed to be possible. As a temperature of at least 650 deg. fahr. is required to crack lubricating-oil into gasoline, the possibility of such cracking rarely exists, for the oil seldom if ever reaches so high a temperature.
A good commercial rectifier should, it is stated, strain the dirt out of the lubricating-oil, distil off the gasoline and water diluent, maintain the viscosity of the oil, eliminate the necessity for draining the crankcase so often, increase the oil mileage materially, permit the use of lighter grades of oil the year round, keep the pistons sealed, increase the compression and power, and help to prevent the fouling of the spark-plugs, and, by eliminating the water, prevent the freezing of the oil-pump in cold weather, rusting, and the formation of sulphurous acid and sludge.