Hi, I have a Honda City idsi 2004 model. It is in very good condition but its avergae dropped from 17 per KM to 13 km per litres. I got it checked and tunning was done, engine head valves were faulty and got them repaired too. But Avergae only improved to 14 per km... long route ( Islamabad). Its orginal reading is 190,000/- What should i do to get the 17km per litre average back? Also my mechanic told me to use engine oil 20w 50 (shell). Which oil should be recommended and what should i do to get the avg back
