2004 Mercedes SL-Class Owner's Manual - Page 391

Technical data Fuels, coolants, lubricants, etc. Using mixtures of Ethanol and Methanol is not allowed. Gasohol, which contains 10% Ethanol and 90% unleaded gasoline, can be used. These blends must also meet all other fuel requirements, such as resistance to spark knock, boiling range, vapor pressure, etc. Gasoline additives A major concern among engine manufacturers is carbon build-up caused by gasoline. Mercedes-Benz recommends only the use of quality gasoline containing additives that prevent the build-up of carbon deposits. After an extended period of using fuels without such additives carbon deposits can build up, especially on the intake valves and in the combustion area, leading to engine performance problems such as: warm-up hesitation unstable idle knocking/pinging misfire power loss Do not blend other specific fuel additives with fuel. This only results in unnecessary cost and may be harmful to the engine operation. Damage or malfunctions resulting from poor fuel quality or from blending specific fuel additives are not covered by the Mercedes-Benz Limited Warranty. 390