wich engine oil you are using? use low viscosity oil. Now low viscosity oils are recommended from OE manufactures for better consumption. i saw a new suzuki swift owner,s manual. they recommend 0w-20.
Go for any SAE 5w-30 or 5w-40 With ACEA: A1/B1,A3/B3/B4 engine oil. i hope it,ll give you a better fuel consumption.