GM Firebird 1967-1981 Repair Guide

Oil and Fuel Recommendations



See Figures 1 and 2

Click image to see an enlarged view

Fig. Fig. 1: When filling the engine with oil, make certain to use the correct viscosity, as shown in this chart

Click image to see an enlarged view

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

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 SE" or better (SF, SG and SH) should be used. Oils of the SE type and better perform a variety of functions inside the engine in addition to the 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 the side of the oil bottle.

For recommended oil viscosities, refer to the accompanying chart.

Non-detergent or straight mineral oils should not be used in your car.


All 1967-74 Firebirds are designed to run on either regular or premium grade fuel depending upon the particular engine's compression ratio. All engines having a compression ratio of 9.0:1 or less can run efficiently on regular gasoline, while any engines with a higher ratio must use premium fuel. All 1975 and later models have been designed to run on unleaded fuel. The use of a leaded fuel in a car requiring unleaded fuel will plug the catalytic converter and render it inoperative. It will also increase exhaust backpressure to the point where engine output will be severely reduced. In all cases, the minimum octane rating of the unleaded fuel being used must be at least 91 RON (87 CLC). All unleaded fuels sold in the U.S. are required to meet this minimum rating.

The use of a fuel too low in octane (a measurement of anti-knock quality) will result in spark knock. Since many factors such as altitude, terrain, air temperature and humidity affect operating efficiency, knocking may result even though the recommended fuel is being used. If persistant knocking occurs, it may be necessary to switch to a higher grade of fuel. Continuous or heavy knocking may result in engine damage.

Your engine's fuel requirement can change with time, mainly due to carbon buildup, which will in turn change the compression ratio. If your engine pings, knocks, or runs on, switch to a higher grade of fuel. Sometimes just changing brands will cure the problem. If it becomes necessary to retard the timing from the specifications, don't change it more than a few degrees. Retarded timing will reduce power output and fuel mileage, in addition to increasing the engine temperature.


If you plan to drive your car outside the United States or Canada, there is a possibility that fuels will be too low in anti-knock quality and could produce engine damage. Send to Pontiac Owner Relations Department the Vehicle Identification Number, compression ratio of your engine and the countries in which you plan to operate and they will send you details of adjustments or modifications that can be made to your engine. It is also wise to consult with local authorities upon arrival in a foreign country to determine the best fuels available.