Assalamolikum WR WB
My budget is 800K and I want to buy a corolla.
I am confused between xli and 2OD diesel.I am a Mehran user so I am very touchy about fuel and maintenance price of diesel and petrol is almost same but doesnt diesel give more mileage than xliwhich one of these two is better?

2-while buying a used car how can one evaluate it's condition(engine performance,body etc)?what should be the main focuses while taking test drive?

3-if driving at low rpm gives high mileage then why does mileage improves on motorway where we all drivearound 100kms with rpm at 3.5-4.and in the cities where rpm rarely crosses 3,mileage appears to be at possibly lowest figure.why is it so?