Petrol challenges diesel on high octane
Am luck enough to have a 6 month old Giulietta 1.4 Turbo Lusso with TCT transmission.
Recently completed over 1000 miles from London to Fife and back (not most direct route).
On Motorways I cruised at 69 or 70mph on cruise control wherever possible.
On first tankful (over 500 miles) I averaged 47.5mpg. I had filled car with Shell Super high octane (97/8?).
On return journey I used normal unleaded 95 Octane (branded Esso).
My return average was 43.5 mpg
Part of this 10% lower consumption was due to possible tail/head winds (not much wind) and part due to more non motorway miles and a 5 mile climb up the Struggles Pass with DNA set to "dynamic" (otherwise set to normal). In my view at least 5% of the difference was due to the increased octane Petrol. In a highly sophisticated engine such as the twin air, turbo, it should be able to advance the ignition or increase the boost to take advantage of the absence of pinking. Saab achieved that in 1990.
Makes the extra cost of Super Unleaded worthwhile and the overall level of economy pretty close to diesel levels. Because Diesel is more dense than petrol, (about 7%) there is less Carbon in each "gallon" and so the CO2 emission figures should show even better improvement.
and its much more fun to drive than the diesel - - even the Alfa one!