[dep]

my best overall consumption came from a non turbo small diesel (1750 Fiesta).
I have now driven 5 turbo diesels and none can match the consumption I used to get from my Sunbeam Sport (the standard factory tuned version of the Hillman Imp) where I could regularly get better than 50mpg while averaging over 50MPH on the whole journey (and no motorways/dual carriageways).
I once got 63mpg from that 1974 car (yes, almost 400 miles from a 6gallon tank and some of it on single track roads in the North West Highlands).

Modern petrol engined technology and all it's clever anti-tamper devices seems unable to match the old fashioned petrol engine with it's good drivability and consumption. That "imp" engine would rev cleanly from 500rpm to 7000rpm. I kept it for 16years.
The direct injection (often referred to as common rail) diesel does offer better consumption, but most manufacturers have used the extra torque and power that is available to turn their products into high performance saloons rather than major on saving the planet.

Small, three cylinder, direct injection, non turbo diesels offer the best chance to obtain very good fuel consumption. But we have to overcome the bad publicity the press keeps heaping on diesel and convince the manufacturers that we want non turbo vehicles.