To obtain the greatest economy from the cylinder of a gasoline engine, the temperature should be as high as possible to permit of successful running and proper lubrication. This necessitates the use of a cylinder oil which has good lubricating qualities and will withstand a high fire test. The oil should contain but little carbon, and yet have sufficient body and vicosity to maintain a close film of oil around the piston.

When operating on a heavy load and the explosions occur at more frequent intervals, a little judgment and experience are required to keep the cylinders from getting too hot, and an occasional cleaning of the piston and ring grooves may be necessary, as these often become clogged with burnt carbon.

Of the two methods of circulating the cooling water - viz., depending on the difference in temperature of the water or a circulating pump-the latter gives the best results and a more uniform temperature of water can be maintained. When using a natural circulation, the water in the cylinder is apt to remain inactive for a time until steam is generated, when it will be forced over into the tank and a quantity of cooler water will be taken into the cylinder to be overheated, as the previous supply. Such a condition would cause an uneven temperature in the water, with less efficient results. A forced circulation would keep the water immediately around the cylinder from reaching the boiling point, and if a throttle valve were installed, a uni. form temperature of, say 165° F., could be maintained.

If the water shows a tendency to get too hot, a freer circulation would cool it to the desired point, and vice versa.

When using natural circulation, a large tank is preferred, and this should be filled to the mouth of the return pipe, so that a slight change in the temperature of the cooling space will cause an immediate flow of water from the tank.

Improper cooling will result in the waste of much fuel, and too cool a cylinder will have the same effect, Thus over cooling as well as over heating should be guarded against for efficient operation of the engine.