I have just bought a Mondeo with a 2.5 litre turbocharged engine. This is the first time that I have owned a car with a turbocharged engine. I have occasionally read in your column in the Saturday Telegraph comments on how such an engine should be treated at the end of a run, i.e., that the engine should be left running for a while to let the turbo 'simmer' before shutting down. Most of my weekly running consists of a 25-mile daily round trip commute to work and variable mileage in the weekend, supermarket, garden centre, etc. I only do the occasional bit of motorway driving. My daily commute consists of a mix of residential and town roads with some faster country roads where 60 mph can be maintained for two or three miles at a time. Can you please gives me some 'rules of thumb' as to when I should let the engine idle before shutting down and when I can reasonable turn it off immediately on arrival?