Petrol has always been a lesser polutant than diesel.

Lorrys etc. use diesel because nobody has yet made a petrol engine that can carry the weights that large lorries/buses carry.

For example, to replicate the amount of torque that a 3 ltr diesel engine develops you would need about a 16ltr petrol engine.

3ltr diesel engine in a truck gives about 15 mpg whereas a 16ltr petrol engine would give about 2mpg.

The fuel, however, is not the real issue.

Any car/lorry/bus uses more pollutants to make it than it will produce in its whole working life.

For a car to be carbon neutral it would need to be super reliable to drive the necessary mileage to recoup the pollution it generated when it was made.

The latest figures say that a little 1ltr petrol engined car would need to complete 1 285 345 miles to become carbon neutral.