Q. Diesel or unleaded? Which is the greenest type of car in terms of emissions?

A. Petrol cars emit fewer health-damaging particulates (e.g. PM5s) but diesel cars emit less global warming carbon dioxide, which would seem to leave liquid petroleum gas (LPG) cars the clear winners!

A. Not so. A diesel car fitted with a particulate 'trap' matches the environmental performance of a 100% LPG car. Sadly, most 'LPG' cars in the UK are, in fact, 'dual fuel', using petrol to start up. As most car journeys are very short this makes quite a difference, leaving diesels fitted with a 'trap' very slightly ahead.