| A | Sump |
|---|---|
| B | Oil Pump |
| C | Crank-case |
| D | Troughs for Oil |
| E | Connecting Rods |
| F | Oil Cups |
| G | Main Bearings |
| H | Crank Pin Bearings |
| I | Cylinders |
| K | Pistons |
| L | Wrist Pins |
| M | Basin in which Crank Shaft Gear Runs |
| N | Piston Rings |
| O | Oil Pockets |
| S | Drain Cock or Oil Gauge |
| T | Push Rods |
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.