2007 Mercedes R-Class Owner's Manual - Page 543

Technical data Fuels, coolants, lubricants, etc. Gasoline additives (gasoline engine) 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 In areas where carbon deposits may be encountered due to lack of availability of gasolines which contain these additives, Mercedes-Benz recommends the use of additives approved by us for use on Mercedes-Benz vehicles. Refer to Factory Approved Service Products pamphlet for a listing of approved product(s). Follow directions on product label. Do not blend other specific fuel additives with fuel. This only results in unnecessary costs and may be harmful to the engine operation. Damage or malfunction resulting from poor fuel quality or from blending additional fuel additives other than those tested and approved by us for use on Mercedes-Benz vehicles listed in the Factory Approved Service Products pamphlet are not covered by the Mercedes-Benz Limited Warranty. Fuel requirements Gasoline engine Only use premium unleaded fuel. The octane number (posted at the pump) must be 91 min. It is an average of both the Research (R) octane number and the Motor (M) octane number: (R+M)/2). This is also known as the ANTI-KNOCK INDEX. Unleaded gasoline containing oxygenates such as ethanol, IPA, IBA and TBA can be used provided the ratio of any one of these oxygenates to gasoline does not exceed 10%; MTBE must not exceed 15%. The ratio of methanol to gasoline must not exceed 3% plus additional cosolvents. Using mixtures of ethanol and methanol is not allowed. Gasohol, which contains 10% ethanol and 90% unleaded gasoline, can be used. 542