Hi Fiona,

Rule of thumb is between 15,000- and 20,000km a year, but it’s not quite that simple. Even if you’re doing relatively high mileage, if you’re mostly just nipping around town you’re still better off with a petrol car. The issue with a lot of diesels is that their particulate filters get clogged if they don’t heat up properly. A long run on the motorway does the job, but just pootling around town won’t put the engine through a proper heat cycle.