My 60K driven vario gives arnd 8km/ltr with AC in khi city.

Got new plugs lately, from super autos and got them fixed frm enercon.
The 8km/lts is the mileage with the new plus previosuly i used to get arnd 10kms/ltr.

Wat cud be the issue? plugs? setting? i think plugs shud not be the issue as i got the NGK plugs from a reputable store plus got, help needed plz.