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Fill the oil reservoir to the proper level with a well refined oil of the viscosity recommended above.
The Oil Gauge Rod, Figure 315, is marked "Full" and "Low." These notations have broad arrows pointing to the level lines.
The oil level should be maintained between these two lines, neither going above the "Full" line nor under the "Low" line. Check the height of the oil level frequently and add oil when necessary.

Oil Gauge Rod

It is good insurance to drain the crankcase —when hot — after the first 500 miles and refill to the proper level with fresh oil.

The frequency with which the oil should be changed, subsequent to the change at the end of the first 500 miles, is governed by the mechanical condition of the car and on how carefully you, as a driver, handle it and care for it.
Oil changes may be required more frequently in the winter than in summer, due to the necessity for using the choke during the winter months. The excessive use of the choke causes crankcase dilution.
We do not recommend the use of so-called re-refined oils, as we find that unless extreme care is used in the refining process, they are wholly unsuited for use in Chevrolet engines.

S. A. E. Viscosity Numbers
The viscosity of a lubricant is simply a measure of its body or fluidity. The S. A. E. viscosity numbers constitute a classification of lubricants in terms of viscosity, or fluidity, but without reference to any other characteristics or properties.
THE REFINER OR MARKETER SUPPLYING THE OIL IS RESPONSIBLE FOR THE QUALITY OF ITS PRODUCT. THEIR REPUTATION IS THE CAR OWNER'S BEST INDICATION OF QUALITY.
The S. A. E. viscosity numbers have been adopted by practically all oil companies and no difficulty should be experienced in obtaining the proper grade of lubricant to meet seasonal requirements.
Crankcase Dilution
A phase of engine oil deterioration, probably the most serious of all, is that of crankcase dilution.
By crankcase dilution, we mean a thinning of the oil on account of certain portions of the gasoline or fuel leaking by the pistons and rings and mixing with the oil.
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Leakage of fuel, or fuel vapors, into the oil reservoir mostly occurs during the "warming-up" period when the fuel is not thoroughly vaporized and burned.

Automatic Control Devices
To Minimize Crankcase Dilution
Your Chevrolet engine is equipped with automatic devices which aid greatly in minimizing the danger of crankcase dilution.
Rapid warming up of the engine is aided by the thermostatic water temperature control which automatically prevents circulation of the water in the cooling system until it reaches a pre-determined temperature.
Thermostatic heat control on the exhaust manifold which, during the warming-up period, automatically directs the hot exhaust gases against the center of the intake manifold, greatly aiding the proper vaporization of the fuel.
The down-draft carburetor is an aid to easy starting, thereby minimizing the use of the choke. Sparing use of the choke reduces danger of raw, or unvaporized, fuel entering the combustion chamber and leaking into the oil reservoir.
An efficient crankcase ventilating system drives off fuel vapors and aids in the evaporation of the raw fuel and water which may find its way into the oil reservoir.

Control by Car Owner Under Abnormal Conditions
Ordinarily the above automatic control devices will minimize, or eliminate, the danger of crankcase dilution.
However, there are abnormal conditions of service when the car owner must aid in the control of crankcase dilution.
Short runs in cold weather, such as city driving, do not permit the thorough warming up of the engine nor the efficient operation of automatic control devices.
It is recommended that the oil be changed more often when the car is subject to this type of operation.
Poor mechanical condition of the engine, such as scored cylinders, poor ring fit, "sloppy" or loose pistons, and faulty valves, poor ignition and incomplete combustion of fuel will increase crankcase dilution.
Keep your car in good mechanical condition.
Poor fuels which contain portions hard to ignite and slow burning will increase crankcase dilution. Use good fuel.