Fuel quality is, as Stewart says, ever more critical.
An interesting example is the difference in MPG we get with
's Merc; it has a 3L V6 turbo diesel (OM642) and puts out 261 bhp and 460 ft lbs.
Fuel consumption, Urban and Motorway
Tesco...............32 to 38mpg
Esso or Shell.......38 to 40mpg
Shell or BP "super".42 to 48mpg
Average over the last 3000 miles is 35mpg. Interestingly this is almost the same as I get from my BMW 2L GDI petrol engine....33.5mpg. When the lower cost of petrol is factored in, together with the longer service interval, the petrol car is cheaper to run. But not as much fun to drive. The Merc is a torque monster...actually more torque than the Plus 8!
The BMW mpg seems not to vary with fuel grade, I use standard shell as it is the cheapest here, now 119p a gallon from Waitrose, Quite why the diesel mpg should vary so much is beyond me, but I've seen this repeatedly over 3 years.
We no longer use Tesco diesel!
