I hv a Nissan Wingroad and it does 10-10.5 in City (colombo trafic) and 15Km out of Colombo. My RPM is allways between 1-1.6 the Max. For it to go at 2500 you must be running at the 3rd Gear.
I also use a fuel efficent unit fixed to the Air Chamber. Its from Jappan.