I'm trying to help my dad by a new car car we are looking at Ford Focus and Volkswagen Golf.

I've tried to talk him into getting a diesel but on 2 separate occasions salesmen have advised us away from diesel. They say it's because my dad only does 5000 miles a year with lots of short trips - they say because new diesels have particulate filters that need to get hot to burn off carbon deposits, and that, if temperatures aren't reached, deposits build up and engine will go into safe mode.

Is this true or are they just trying to sell petrol cars as diesels have become more popular?