distilled in a vacuum in order that the light distillates, such as the fuel oils, will be separated from the crude petroleum base obtained from Pennsylvania wells at low temperatures and then filtering the oil through charcoal to remove free carbon and other impurities it contains. The greater the number of times the oil is filtered the lighter it becomes in color and body. The best cylinder oils are obtained in three grades: light, which has a consistency slightly greater than machine oil; medium, which is somewhat heavier than the light and is an intermediate grade between that and the heavy bodied oil which has the consistency of warm molasses. The light and medium oils are used on power plants having closely fitting pistons and bearings, while the heavy lubricants are used in air cooled engines and in power plants that have become worn to such an extent that the cushioning properties of the heavier bodied oils are desirable. Any pure hydro-carbon oil, having a high degree of viscosity at 100 degrees F., having a vaporizing point of about 200 degrees F., a flash point between 425 and 500 degrees F., and a fire test of 600 degrees F. or over, will be suitable for use in gas engine cylinders.

Q. How are the various portions of an automobile lubricated? A. The power plant of an automobile is usually lubricated by some means that will insure a continued supply of lubricant to the interior parts of the engine and that will supply the oil in quantities that will compensate for any loss through vaporizing or burning in the combustion chamber or leakage. The change speed gearset, differential gearing, universal joints and axle bearings are generally packed with a semi-fluid grease that remains in place and that does not need renewing frequently. Spring shackles, brake rod ends, and similar parts are greased by compression grease cups, which may be screwed up from time to time to inject more lubricant between the bearing surfaces or by means of small oil cups which demand periodical attention and filling from the usual form of hand oil can or syringe.

Q. Describe simplest method of oiling gas engine parts.

A. The interior of gasoline engines of the closed base form may be oiled by putting in a certain quantity of lubricant in the engine base

until it rises to such a height that it will be splashed around the inside of the motor by the revolving connecting rod lower end or by counter weights or enclosed flywheel. On open base engines (never used in automobiles) the main bearings are lubricated by compression grease cups in many cases and the connecting rod by oil from a small sight feed oil cup directly attached to the crank pin bearing. A similar member of larger capacity serves to oil the piston and cylinder walls. The open base form of motor is never used in automobile practice though it has received wide application in the stationary power plants and is used to some extent in marine service.

Q. What is a sight feed lubricator?

A. The gravity sight feed lubricator is seldom used at the present time in automobiles. The first sight feed devices included a container for the lubricant having glass walls, so the amount of oil it held could be readily ascertained at any time, communicating with a lower chamber, also having glass walls, by means of a needle valve controlled orifice. The valve could be adjusted to feed any desired number of drops of oil per minute and the flow of oil could be stopped at will without changing the adjustment of the needle valve by shifting a small lever that allowed the valve to drop under slight spring pressure until it closed the passageway communicating to the small sight feed chamber beneath the main container which was piped to the point needing the lubricant. As a general rule gravity oil cups are applied directly to the parts needing oil and are generally used on cheaper marine and stationary engines.

Q. What is a compression or pressure feed lubricator?

A. A typical pressure feed lubricator is outlined at Fig. 116. This consists of a small tank holding one or two quarts of oil, which is attached to the motor at any convenient point and which is designed so the oil it contains may be put under pressure and forced through a pipe to a sight feed manifold fitting from which the individual oil leads go to the points needing oil. The pressure is usually obtained from the exhaust or by a pipe leading to the crank case interior. A small check valve fitting is carried at the end of the pressure pipe on the oil container in such a way that the air or gas under pressure will raise the check valve from its seat and flow

into the oil container. As the check valve seats when the pressure of gas in the tank is sufficiently high the confined gases cannot escape and must force the oil out of the tank. The oil flows to the top of the sight feed arrangement where the amount dropping can be regulated at will and as the manifold is always carried higher than the bearing point the oil flows principally by gravity assisted to some extent by a slight pressure escaping from the oil container. As a lubricator of this nature will supply lubricant as long as there is pressure in the tank and as no oil is needed after the engine

Fig. 116.-Simple Compression Feed Oiler in Which Oil is Supplied From Container by Crank Case or Exhaust Pressure.

stops it is desirable to fit the container with a small petcock or relief valve which can be opened when the engine is stopped to relieve the pressure on top of the oil and thus interrupt the supply to the bearings.

Q. Name principal methods of mechanical oiling and state their advantages.

A. There are two main methods of oiling a power plant by mechanical means, the most common one involving a single pump which keeps the oil in circulation from the oil sump or container integral

with the crank case to the crank compartments, where it is picked up by the connecting rods and splashed around. The other is by individual lead sight feed oiler in which each separate bearing is supplied by its own pump plunger through an oil tube. A defect of the sight feed gravity oiling method is that the flow of oil might be stopped by any small particle of foreign matter in the oil tube or even by thickening of the oil due to lowering temperature so the bearing points would be deprived of lubricant.

Much trouble resulted from this source and positive systems by which oil must be delivered to the bearing points as long as the power plant is kept in operation were evolved. With a powerful pump

Haynes Car.

forcing the lubricant through the oil supply tubes it is difficult for any accumulation of lint or small piece of wax carried by the oil itself to constrict the bore of the tube and retard the flow of lubricant. The pumps have sufficient pressure so the oil, which is an incompressible liquid, will be forced to the bearing points and clear the tube or passage of obstructions tending to impede its flow. The individual lead form of oiler or mechanical oiler having a large number of individual pumps is seldom used at the present time as practically all automobile engineers favor the simpler and more positive self-contained systems.

Q. Describe action of constant level splash system.

A. The arrangement of the crankcase interior, when used in connection with a constant level splash system, is clearly outlined at Fig. 117. As will be evident the crankcase is divided into two parts, the lower portion or sump being separated from the upper part in which the crankshaft revolves by a cast partition wall of corrugated form which practically divides the interior into four compartments, one for each connecting rod. A small standpipe extends from each compartment to a sufficient height so any accumulations of oil that would tend to raise the level of lubricant above the predetermined point will overflow and pass back from the crank

Fig. 118. Methods of Supplying Oil to Bearings.

A-Oil Pocket Above Main Bearings Which Collects Lubricant. B-Showing Scoops at Bottom of Connecting Rod to Pick Up Lubricant From Troughs in Crankcase.

compartments to the sump beneath them. The main bearings are oiled as shown at Fig. 118-A. The oil accumulates in the oil troughs shown at Fig. 118-B and is picked up by scoops attached to the lower connecting rod bearing cap and splashed around the interior of the crankcase. The spray or oil mist collects on all working parts and a portion of the oil will be caught by oil pockets such as shown at A and diverted to the bearing, while some of the lubricant will be splashed on the cylinder walls where it will be spread out and