if you mostly do short runs around town where the engine doesn't warm up, then petrol would probably be better for you. BUT with most cars now moving to smaller engines, when we last trialed a Nissan Qashqai petrol, is was firkin awful, 5 speed box, and geared to rev the little 1.4 engine - apparently this is good for fuel efficiency. Took it up the local dualcarriage way and spent 20 miles looking for another gear. After years of 2 litre diesels it was awful. We ended up with the diesel version, and this topic has reminded me it's time to give it a good blast and clear the particle filter out