Chevrolet Blazer/Jimmy 1969-1982 Repair Guide

Fuel and Engine Oil Recommendations




All engines through 1971 are designed to use fuel of 91 research octane or higher. All 1972 and later engines, except those with a catalytic converter, use unleaded or low-lead fuel. All engines with a catalytic converter must use unleaded fuel.

Your engine's fuel requirement can change with time, mainly due to carbon buildup changing the compression ratio. If your engine pings, knocks, or runs on, switch to a higher grade of fuel and check the ignition timing as soon as possible. If it is necessary to retard timing from specifications, don't change it more than about four degrees. Retarded timing will reduce power output and fuel mileage and increase engine temperature.

Should you plan to operate your Blazer or Jimmy in a foreign country, you can contact the Chevrolet or GMC Owner Relations Department to obtain information on required engine modifications or adjustments and the quality of the fuels available there. Be sure to supply your vehicle's Vehicle Identification Number (VIN) and the engine's compression ratio if available.


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Fig. Fig. 1 Gasoline engine oil viscosity chart

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Fig. Fig. 2 Look for the API oil identification label when choosing your engine oil

Only oils labeled SE/SF are approved under warranty for use in 1972 and later models. Oils labeled SD were approved for 1971 and earlier models, since the higher quality SE rated oils were not generally available at that time. SE/SF oils should now be used in all models. Non-detergent oils are specifically not recommended. You can find the SE/SF marking either on the top or on the side of the oil container; the viscosity rating should be in the same place. Select the viscosity rating to be used by your type of driving and the temperature range anticipated before the next oil change.

The multi-viscosity oils offer the important advantage of being adaptable to temperature extremes. They can allow easy starts at low temperatures, yet still give good protection at high speeds and warm temperatures. This is a decided advantage in changeable climates or in long distance touring.



Fuel makers produce two grades of diesel fuel, No. 1 and No. 2, for use in diesel engines. Generally speaking, No. 2 fuel is recommended over No. 1 for driving in temperatures above 20° F. In fact, in many areas, No. 2 diesel is the only fuel available. By comparison, No. 2 diesel fuel is less volatile than No. 1 fuel, and gives better fuel economy. No. 2 fuel is also a better injection pump lubricant.

Two important characteristics of diesel fuel are its cetane number and its viscosity.

The cetane number of a diesel fuel refers to the ease with which a diesel fuel ignites. High cetane numbers mean that the fuel will ignite with relative ease or that it ignites well at low temperatures. Naturally, the lower the cetane number, the higher the temperature must be to ignite the fuel. Most commercial fuels have cetane numbers that range from 35 to 65. No. 1 diesel fuel generally has a higher cetane rating than No. 2 fuel.

Viscosity is the ability of a liquid, in this case diesel fuel, to flow. Using straight No. 2 diesel fuel below 20° can cause problems, because this fuel tends to become cloudy, meaning wax crystals begin forming in the fuel. In extreme cold weather, No. 2 fuel can stop flowing altogether. In either case, fuel flow is restricted, which can result in a "no start" condition or poor engine performance. Fuel manufacturers often "winterize" No. 2 diesel fuel by using various fuel additives and blends (No. 1 diesel fuel, kerosene, etc.) to lower its winter-time viscosity. Generally speaking, though, No. 1 diesel fuel is more satisfactory in extremely cold weather.

No. 1 and No. 2 diesel fuels will mix and burn with no ill effects, although the engine manufacturer will undoubtedly recommend one or the other. Consult the owner's manual for information.

Depending on local climate, most fuel manufacturers make winterized No. 2 fuel available seasonally.

Many automobile manufacturers publish pamphlets giving the locations of diesel fuel stations nationwide. Contact the local dealer for information.

Do not substitute home heating oil for automotive diesel fuel. While in some cases, home heating oil refinement levels equal those of diesel fuel, many times they are far below diesel engine requirements. The result of using "dirty" home heating oil will be a clogged fuel system, in which case the entire system may have to be dismantled and cleaned.

One more word on diesel fuels. Don't thin diesel fuel with gasoline in cold weather. The lighter gasoline, which is more explosive, will cause rough running at the very least, and may cause extensive engine damage if enough is used.


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Fig. Fig. 3 Diesel engine oil viscosity chart

Use ONLY engine oils labeled with the A.P.I. (American Petroleum Institute) designation "SF/CD" or "SF/CC". Do not use any other type of oil. The A.P.I. designations are listed somewhere on the oil can, usually on the top or label. The A.P.I. has several designations, such as: SC, SD, SE, CB, CC, CD.

Several different designations may appear on the can. Be sure the oil used has either "SF/CD" or "SF/CC" designations, regardless of the order in which they appear on the oil can.

Using any type of oil other than "SF/CD" or "SF/CC" may affect warranty.

Do not use engine oils labeled only SE or only CC. These oils will not give the protection and lubrication of diesel engine needs. When reading the container, be sure not to confuse the SE designation with the letters "SAE," which may also appear on the can.


Do not use any supplemental additives. Using oil additives may cause engine damage and may affect warranty.


Engine oil viscosity (thickness) has an effect on fuel economy. Lower viscosity engine oils can provide increased fuel economy; however, higher temperature weather conditions require higher viscosity engine oils for satisfactory lubrication. The chart on page 23 lists the engine oil viscosities that will provide the best balance of fuel economy, engine life, and oil economy.