In stop start traffic my diesel is barely any more efficient than my old petrol 530i. On a run it's considerably better.
Thanks for confirming its more efficient which was my point

I didn't say massively more, just more.
But real world the main benefit of diesel is cruising and that only really happens on main roads, as soon as you add in accelerating the MPG drops, and its hard to drive diesel as efficiently when accelerating as most people tend to gun them a bit harder to get acceptable performance. Drive an old non turbo diesel to see how MPG was far higher in that sort of situation, but also how they are terribly slow, then you realise how the turbo changed the performance.
I assume like most people you 5 seater is also mainly carrying you so petrol is less impacted.
When you load up a car with 5 people and a few suitcases etc the petrols will suffer more than the diesels.
Edit to add an example, numbers a bit out of date so not refelcting latest duty etc, but I think this highlights why people will still be drawn to diesel. Buying a £20k car but worrying about saving £300 a year, and the £300 a year highly dependant on the residual value of the diesel
Petrol:
- Golf Match 1.4 TSI 122hp – £19,100
- Value after 3 years – £7,640 (40% of new car price)
- Fuel economy, urban – 34.4 mpg
- Fuel economy, combined – 45.6 mpg
- Road tax (first year included in new car price) – £130/year
Diesel:
- Golf Match 2.0 TDI 140hp – £21,090
- Value after 3 years – £9,491 (45% of new car price)
- Fuel economy, urban – 46.3 mpg
- Fuel economy, combined – 58.9 mpg
- Road tax (first year included in new car price) – £95/year
So the diesel car is more expensive by nearly £2,000 when new, but should be worth about £1,800 more after three years. It costs less to register (£35/year at present, so not a lot in it) and should use less fuel on average.
Total cost of buying and running each car for three years (excluding insurance, servicing and maintenance) are as follows:
Petrol:
- Using Urban fuel economy figures – £17,335
- Using Combined fuel economy figures – £15,964
Diesel:
- Using Urban fuel economy figures – £16,293
- Using Combined fuel economy figures – £15,300
So the diesel Golf is £347/year cheaper to run using the urban figures, and £221/year cheaper to run using the combined figures. In the overall of a £20,000 car, this is hardly a significant difference, and doesn’t take into account individual driving circumstances. The government fuel economy tests are not really representative of real-world driving, and very few drivers ever match the official figures. Below I will detail the differences in the way a petrol engine drives compared to a diesel engine.
shamelessly ripped from
http://www.thecarexpert.co.uk/fuel-economy-petrol-or-diesel/