My friends, having 1.6 in my office, claim 10-10.5 in city with AC. ..amd btw , i m in Lahore. Overall driving style matters. Oil wont do anything...at all in a new car. I may feel harsh but...i m using taglon and constantly getting 11.3- 11.8 ( tank to tank), as i don't believe mileage meter. Although Corolla's mileage meter is much better than what I found in city.
Oil grades are more of a speculation..as the effect it makes is very small and eventually everything comes down to driving style. Difference may be more prominent in smaller engines. I tried so much with city and mostly changing brands is personal thinking. I personally will switch to quartz 9000 from Taglon but that's due to unjustifiable high cost of Taglon and brand satisfaction from Total..only