Driving and operating 127ActivationWhen reverse gear is engaged, thesystem switches itself onautomatically.The system can also be activated atlow speed by pressing the r button.An obstacle is indicated by buzzers.The interval between the buzzersbecomes shorter as the vehicle getscloser to the obstacle. When thedistance is less than 30 cm (1 ft), thebuzzer is continuous.9 WarningUnder certain circumstances,various reflective surfaces onobjects or clothing as well asexternal noise sources may causethe system to fail to detectobstacles.DeactivationDeactivate the system by pressingthe r button.The system automatically switchesitself off when reverse gear isdisengaged.Towing equipmentThe system automatically detectsfactory-fitted towing equipment.The rear parking sensors aredeactivated when towing.FuelFuel for petrol enginesOnly use unleaded fuel that complieswith DIN EN 228.Fuels with ethanol content greaterthan 5 % may only be used if thevehicle has been specificallydeveloped and approved for thesefuels.Use fuel with the recommendedoctane rating 3 186. Use of fuel withtoo low an octane rating can reduceengine power and torque and slightlyincreases fuel consumption.CautionUse of fuel with too low an octanerating could lead to uncontrolledcombustion and engine damage.Fuel for diesel enginesOnly use diesel fuel that complieswith DIN EN 590. The fuel must havelow sulphur content (max. 50 ppm).Equivalent standardised fuels with
