BMW Coupes and Sedans 1970-1988 Repair Guide

Fuel and Engine Oil Recommendations


FUEL Gasoline Engines

For the years 1970-74, premium grade fuel is recommended. The actual octane required varies with the year and vehicle model.

For the years 1975-79, octane requirements are standardized at 87 AKI (which means "Anti-Knock Index"), which is an average of "Motor" and "Research" octane ratings. All BMWs made in the 1975-79 model years, except the 528i, recommend the use of regular, leaded fuel. Since this type of fuel is no longer available, high octane unleaded fuel is suggested as a suitable alternative.

The 528i, and all 1980 and later models have been designed to run on unleaded fuel. In all cases, the minimum octane rating of the unleaded fuel being used must be at least 91 RON (87 CLC). Al unleaded fuels sold in the US 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 persistent knocking occurs, it may be necessary to switch to a high 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.

Diesel Engines

No. 2 automotive diesel fuel with a cetane rating of 40 is sufficient for most localities. In colder areas, No. 1 can be used during periods of extreme cold.


See Figures 1 and 2

Gasoline Engines

The Society of Automotive Engineers(SAE) 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 temperature 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 American Petroleum Institute(API) designation indicates the classification of engine oil used under certain given operating conditions. Only oils designated for use "Service SF" should be used. Oils of the SF 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.

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

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Fig. Fig. 1: Recommended oil viscosity for given temperatures

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

Diesel Engines

Engine oil, meeting API specification SF/CD is recommended. You can use either SAE 30W or SAE 10W-40 weight oils.