GM Caprice 1990-1993 Repair Guide

Fuel and Engine Oil Recommendations


Engine Oil

See Figure 1

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Fig. Fig. 1: Engine oil viscosity recommendation

The SAE (Society of Automotive Engineers) grade number indicates the viscosity of the engine oil and thus its ability to lubricate at a given temperature. The lower the SAE grade number, the lighter the oil; the lower the viscosity, the easier it is to crank the engine in cold weather.

Oil viscosities should be chosen from those oils recommended for the lowest anticipated temperatures during the oil change interval.

Multi-viscosity oils (10W-30, 20W-50 etc.) offer the important advantage of being adaptable to temperature extremes. They allow easy starting at low temperatures, yet they give good protection at high speeds and engine temperatures. This is a decided advantage in changeable climates or in long distance touring.

The API (American Petroleum Institute) designation indicates the classification of engine oil used under certain given operating conditions. Only oils designated for use Service SG, SG/CC or SG/CD should be used. Oils of the SG type perform a variety of functions inside the engine in addition to their basic function as a lubricant. Through a balanced system of metallic detergents and polymeric dispersants, the oil prevents the formation of high and low temperature deposits and also keeps sludge and particles of dirt in suspension. Acids, particularly sulfuric acid, as well as other by-products of combustion, are neutralized. Both the SAE grade number and the API designation can be found on top of the oil can.

For recommended oil viscosities, refer to the chart.


There are excellent synthetic and fuel-efficient oils available that, under the right circumstances, can help provide better fuel mileage and better engine protection. However, these advantages come at a price, which can be three or four times the price per quart of conventional motor oils.

Before pouring any synthetic oils into your car's engine, you should consider the condition of the engine and the type of driving you do. Also, check the car's warranty conditions regarding the use of synthetics.


The engine is designed to operate on unleaded gasoline ONLY and is essential for the proper operation of the emission control system. The use of unleaded fuel will reduce spark plug fouling, exhaust system corrosion and engine oil deterioration.

In most parts of the United States, fuel with an octane rating of 87 should be used; in high altitude areas, fuel with an octane rating as low as 85 may be used.

In some areas, fuel consisting of a blend of alcohol may be used; this blend of gasoline and alcohol is known as gasohol. When using gasohol, never use blends exceeding 10% ethanol (ethyl or grain alcohol) or 5% methanol (methyl or wood alcohol).

The use of fuel with excessive amounts of alcohol may jeopardize the new car and emission control system warranties.