Hi Margaret,

A diesel engine is theoretically more economical, though in reality that's only of use on longer journeys at higher speeds - i.e. on the motorway - where the diesel engine is at its best. When used predominantly away from that environment, there are components of the diesel engine that can get clogged up and fail - or cost a lot to repair. The rough changeover annual mileage is 25,000km a year - i.e. if you do more than that per annum, and a lot of it is at motorway speed, then it's likley to be worth going for a diesel.

In general, a diesel engine has more low-down 'torque' as well, which means it can push along a heavier car better than a small petrol engine could. That's useful for fully-loaded family cars such as the Verso, for example, but we'd suggest that the potential maintenance costs that come with diesels mean the petrol version will suit most buyers of that car.