We've found tuning the the engine helps, JE engenering tuned my bothers hippo and not only does it go like stink est130-135bhp and LOAD more torque low down. The engine works easier, lot less down shifting it all help reduse consumption (if you can control the right foot and stop burning off boyracers & BMW's). The exta torque is very handy off road as well. Also my 1.8 Asstray (Astra) gets 40mpg and a friends 1.4 only gets mid 30's. Sensible engine = better mpg (eg 1.8 asstray works easier than a gutless 1.4 asstray, sensible tuned TD4 works easier than a standard TD4) Thats my theory any way.