My 1994 Mercedes-benz E320 coupé has done about 100,000 miles and is now mainly used for long distance continental driving in summer. To keep the aircon in condition, I take it for a 20-mile drive every month for the rest of the year. However, in order to avoid salty roads in the winter, is it sensible to let the car tick over on the drive with the aircon running until it is fully warmed up – say, for 30 minutes every month? Allan Luskow The basic recommendation to maintain the air-conditioning system is that it should be operated for at least 10 minutes every month. This is to circulate the refrigerant through the system – the refrigerant carries the necessary lubricants to keep the system in optimum condition, preventing the seals from drying out and subsequently shrinking and leaking.
By giving the vehicle a run, as you have been doing, you are fulfilling these requirements while also ensuring the engine reaches full operating temperature. I can fully understand your reluctance to take your vehicle out when the roads have been salted, as the corrosive substance could get thrown up under your vehicle, causing long-term problems. Running the vehicle once a month stationery and allowing it to reach full working temperature will be the best action to help prevent any problems in the future.
Also, as the vehicle’s fuel will not be replenished during the storage period, it may be worth adding a fuel stabiliser to the tank to prevent the build-up of varnish and deposits in the fuel system.