Guys as far as tyre size is concerned using 185/65 is the best option with 15 inch Rims. This is what I am using and my car has never touched any bumper whether it be too high or no matter how many people are in car.
Secondly as far as which fuel to use, I have tried all 3 brands Total, PSO and Shell. The best results given to me were by Shell (Defence, Modeltown, G1).
Zero knocking and great mileage and the worst fuel was of PSO (Be it any station Cavalry, Defence).
P.S. Fuel type is Super. No high octane. Secondly Shell is the only fuel company which claims it to be unleaded, I dont know about whether PSO and TOTAL fuel is unleaded or not.