AOA, i have been getting excellent mileage on my platz since last one year. ( 225 on long route and 160-170 in city). but since few weeks this has gone down. i have had the car tuned up but to no avail. i guess spark plugs have worn out. or may be it is coz of bad CNG ( by the way i always get tank filled form the same station).
can you guide me for:
1. which plugs would be best for economy,two pole spark plugs or four. and which company... ngk or denso
2. should i get the cng setting readjusted again after tuning?