Mercedes Coupes/Sedans/Wagons 1974-1984 Repair Guide

Oil and Fuel Recommendations


Mercedes-Benz is constantly testing and analyzing fuels and lubricants in an effort to determine which lubricants and fuels are suitable and provide the best service in their vehicles. The recommended fluids and their applications are published by Mercedes-Benz under the title "Specifications for Service Products". It is impossible to detail, in this guide, those materials which are suitable at any given time, since the publication is constantly revised and updated by Mercedes-Benz.

In general, most any high quality material is suitable for the particular application, with the exceptions noted below.


See Figures 1 and 2

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Fig. Fig. 1: Oil viscosity chartgasoline engines

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Fig. Fig. 2: Oil viscosity chartdiesel 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 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 temperature. 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 SE" should be used. Oils of the SE 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 byproducts of combustion, are neutralized. Both the SAE grade number and the API designation can be found on top of the oil can.

Diesel engines also require SE engine oil. In addition, the oil must qualify for a CC rating. The API has a number of different diesel engine ratings, including CB, CC and CD. Any of these other oils are fine as long as the designation CC appears on the can along with them. Do not use oil labeled only SE or only CC. Both designations must always appear together.

For recommended oil viscosities, refer to the chart.

As of late 1980, the API has come out with a new designation of motor oil, SF. Oils designated for use "Service SF" are equally acceptable in your pre-'80 car and should be used exclusively in 1981 and later models.

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


There are many excellent synthetic and fuel-efficient oils currently available that can provide better gas mileage, longer service life, and in some cases better engine protection. These benefits do not come without a few hitches, howeverthe main one being the price of synthetic oils, which is three or four times the price per quart of conventional oil.

Synthetic oil is not for every car and every type of driving, so you should consider your engine's condition and your type of driving. Also, check your car's warranty conditions regarding the use of synthetic oils.

Both brand new engines and older, high mileage engines are the wrong candidates for synthetic oil. The synthetic oils are so slippery that they can prevent the proper break-in of new engines; most manufacturers recommend that you wait until the engine is properly broken in (5,000 miles) until using synthetic oil. Older engines with wear have a different problem with synthetics: they "use" (consume during operation) more oil as they age. Slippery synthetic oils get past these worn parts easilyif your engine is "using" conventional oil, it will use synthetics much faster. Also, if your car is leaking oil past old seals you'll have a much greater leak problems with synthetics.

Consider your type of driving. If most of your accumulated mileage is high speed, highway type driving, the more expensive synthetic oils may be of benefit. Extended highway driving gives the engine a chance to warm up, accumulating less acids in the oil and putting less stress on the engine over the long run. Under these conditions, the oil change interval can be extended (as long as your oil filter can last the extended life of the oil) up to the advertised mileage claims of the synthetics. Cars with synthetic oils may show increased fuel economy in highway driving, due to less internal friction. However, many automotive experts agree that 50,000 miles is too long to keep any oil in your engine.

Cars used under harder circumstances, such as stop-and-go, city type driving, short trips, or extended idling, should be serviced more frequently. For the engines in these cars, the much greater cost of synthetic or fuel-efficient oils may not be worth the investment. Internal wear increases much quicker on these cars, causing greater oil consumption and leakage.

The mixing of conventional and synthetic oils is not recommended. If you are using synthetic oil, it might be wise to carry two or three quarts with you no matter where you drive, as not all service stations carry this type of lubricant.

FUEL Gasoline

The fuel requirement (octane rating) for your vehicle is listed in the owner's manual or available from any Mercedes-Benz dealer. In general, since 1974, Mercedes-Benz engines are designed to run on regular gasoline or regular unleaded gasoline if a converter is used. In the event that a fuel of the proper octane rating is not available, the timing can be retarded but this is as an emergency measure only. The proper fuel should be obtained as quickly as possible and the timing should be reset to specifications as soon as possible.

If the timing has been retarded because of low octane fuel, the car should not be driven at high speeds.

Diesel See Figure 3

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Fig. Fig. 3: Diesel engine fuel mixture requirements

Use only commercially available No. 2 or No. 1 diesel fuel. Mercedes-Benz does not recommend the use of marine diesel fuel or heating oil.

At very low temperatures, the viscosity of No. 2 summer diesel fuel may become insufficient (the fuel will not adequately flow); winter diesel fuel should be unaffected as low as approximately 0-F.

If summer diesel fuel clogs at low winter temperatures, a specified percentage of kerosene can be mixed with No. 2 summer diesel fuel to improve its viscosity.

Add kerosene according to the following table, but keep the percentage of kerosene to a minimum since a loss of engine power will likely result. At no time should the % of kerosene exceed 50%. Regular gasoline can be substituted for kerosene, but the amount should not exceed 30%, and it is not recommended to dilute No. 1 diesel fuel.


Since 1974, all Mercedes-Benz automatic transmissions have been of the torque converter type. All use DEXRONreg; B, Type B fluid, of which there are many high quality brands available.


There are many high quality gear lubricants available for use with standard type differentials. Just be sure that the lubricant is specified SAE 90 viscosity for hypoid gears.

Vehicles equipped with a limited slip (positive traction) type differential should use only special lubricant available at Mercedes-Benz dealers. It has special additives for use with limited slip rear axles.


A list of approved lubricants for the hydropneumatic suspension can be found earlier in this section. The 6.9 can use only Aral 1010, available from dealerships.


A 50/50 mixture of water and anti-freeze serves as coolant for Mercedes-Benz engines. Generally tap water meets the requirements for water. It is important that you do not use sea water, brackish water, brine, or industrial waste waters. Also, lime-free water, completely distilled water, rain water, or desalinated water should not be used, as this will only hasten the corrosion process.

In addition, an emulsifying corrosion inhibitor should be used (add a can of corrosion inhibitor every time you change the coolant). This is to combat the effects of rust, scale, and other deposits which tend to reduce the cooling properties of the coolant due to poor heat conductivity.