CHAPTER VI

IF WELL “SLICKED” THE ENGINE RUNS

If we scuff our feet on the bare pavement we wear out our shoes, develop a lot of heat, and notice considerable resistance; but if we step on a banana peel, a piece of ice, or a patch of oil or grease, our passage is facilitated, and our feet are likely to slide out from under us and we sit down with little effort. Now this is just like the auto engine. If the parts were all made perfect and fitted together properly and the engine started without lubrication, there would be so much friction that the parts would very quickly wear out.

As a matter of fact an engine could be wrecked in less than half an hour’s running, unless there were something introduced to prevent friction.

The lubrication of the modern auto engine is so simple that most owners do not realize its importance. It is the things which normally take care of themselves that are most likely to be neglected; the things about which we know the least, when they do go wrong, cause the greatest damage, not the things with which we have become familiar through frequent tinkering.

The instruction books issued by the manufacturers say to inspect the oil reservoir of the engine each time before leaving the garage to see if the required amount of oil is there; and this inspection should not be neglected; with most owners it is “by guess and begorry.”

The most usual scheme of engine lubrication used to-day is to carry a certain amount of oil in a compartment in the bottom of the crank case, called the sump. There is a pump which operates whenever the engine is running and which pumps the oil to some sort of an indicator on the dash, so that the driver can see if it is circulating. From this point it flows by gravity to the splash pans located under the connecting rods, and above the sump. Here the oil is held at such a level that when the crank shaft revolves the ends of the connecting rods dip into the oil and splash it over practically all the working parts of the engine. This splashing and agitation of the oil creates a fog of oil in the crank case, and the rapid motion of the piston and other parts circulates the vaporized oil over the moving members, so that a film of oil is deposited even on those parts where the splash itself does not reach.

The pump circulates more oil than is used and the splash pans are arranged with overflow openings so that the excess simply drops back into the sump and again is passed through the system by the pump.

It is this oil which enables the engine to move without friction. It is the effect of the banana peel under your heel in that it makes the parts slip over each other easily. In addition to this the oil between the piston and the cylinder wall makes a seal which prevents gas from leaking by on compression and explosion strokes. If too much oil is fed a great deal will be drawn past the piston on the suction stroke and get in the cylinder where it will burn, forming carbon and giving out smoke from the exhaust.

In this type of system the principal causes of trouble are too much oil in the sump, so that the level reaches above the splash pans, and projections upon the connecting rods that are so large that too much oil is splashed when the level is normal. In the latter case the trouble often may be remedied by narrowing the projections of the connecting rod which dip into the oil. It is not wise to shorten these projections, because it is very difficult to get an even graduation that will insure sufficient oil without giving too much.

If the oil should run out while the car is in use, the engine will get stiff, lose its power, and the friction of the unlubricated parts will generate sufficient heat to melt out the lining of the bearings, and if the engine runs for any length of time in this condition it may be wrecked beyond repair.

This means that although the oiling system needs very little or no attention, it should be inspected each time before leaving the garage and on the road occasionally if long trips are taken, to make sure that oil is present in sufficient quantity and is circulating.

Oil in a sense does wear out and in this sort of a system it should be replaced with new oil occasionally. Some of it will work up past the piston and be burned up and some will work out around the different parts of the engine and be lost, but most of it will remain in the sump longer than it is advisable to use it. All of the gasoline that is taken into the cylinder is usually not consumed. Some of it is forced past the piston on the compression stroke into the crank case, where it condenses and mixes with the oil. This thins the oil sometimes to a point where it has little or no lubricating value. Also the oil on the inside of the piston head burns and drops down into the crank case, and there is some wear of the moving parts which causes a deposit of metal in the oil. These things, together with the small amount of road dust sucked in through the breather pipe, make the oil in a short time unfit for use.

In this circulating splash system, where the oil is used over and over again, the oil should be drained out entirely about every 1000 miles, more or less, depending upon the grade of the oil and fit of the piston. The following things all enter into the lubricating value of the oil after 1000 miles’ performance:

Grade of the oil Fit of the pistons Temperature at which the engine is run Grade of the gasoline Adjustment of the carburetor.

There are some other things, but the above are the chief factors. It would be well to acquire the habit of examining the oil every few days to determine just how it stands up in the particular engine.

After the oil is drained out, a half gallon or so of kerosene should be poured into the sump and the engine run for about one minute or less, the idea being to get a complete circulation of kerosene through the lubricating system. The kerosene should then be drained off and the splash pans under the connecting rods be wiped out if possible. The screen of the oil pump also should be removed and washed carefully in kerosene and replaced. Then the sump should be filled to the proper level with fresh oil.

Aside from getting under the car to remove the drain plug, this is not a dirty job. Still one would better put on old clothes and overalls to prevent the possibility of getting grease on a perfectly good suit.

While oil is expensive, it is poor economy to use it beyond its useful stage, because damage may be done to the machinery which will cost much more than a year’s supply of good oil.