Most Chevy II and Nova models prior to 1972 are designed to operate on regular grades of fuel commonly sold in the U.S. and Canada.
On 1972-74 models, unleaded or lowlead fuels of approximately 91 octane (Research Octane) or higher are recommended. General Motors recommends the use of unleaded fuels to reduce particulate and hydrocarbon pollutants. In states using the Gasoline Performance and Information system of fuel designation, unleaded or low-lead fuels with an anti-knock designation of "2" or higher are recommended.
Use of a fuel which is too low in anti-knock quality will result in "spark knock." Since many factors affect operating efficiency, such as altitude, terrain and air temperature, knocking may result even though you are using the recommended fuel. If persistent knocking occurs, it may be necessary to switch to a slightly higher grade of gasoline to correct the problem. In the case of late model engines (1972-74), switching to a premium fuel would be an unnecessary expense. In these engines, a slightly higher grade of gasoline (regular) should be used only when persistent knocking occurs. If this will not cure the problem, consult a dealer.
Due to the use of catalytic converters on all 1975 and later Nova models, fuel usage is restricted to unleaded gasoline only.
1975 and later Novas carry the notation "Unleaded Fuel Only" in the center of the speedometer face and near the fuel tank filler. They also have a new fuel tank filler neck that accepts only the small diameter fuel nozzle which is on all unleaded fuel pumps and a threaded gas cap to ensure proper tank sealing.
The SAE grade number indicates the viscosity of the engine oil, or its ability to lubricate under a given temperature. The lower SAE grade number, the lighter the oil; the lower the viscosity, the easier it is to crank the engine in cold weather.
The API (American Petroleum Institute) designation indicates the classification of engine oil for use under given operating conditions. Only oils designated for "Service SH" (old designation MS) should be used. These oils provide maximum engine protection. Both the SAE grade number and the API designation can be found on the label on a quart of oil.
Non-detergent or straight mineral oils should not be used.
Oil viscosities should be chosen from those oils recommended for the lowest anticipated temperatures during the oil change interval.
Do not use SAE 5W-20 oils for high speed driving.