Wa Alaikum Salam. Bro no offense / disrespect (just on a lighter note); if you are going to buy an 1800 cc car, you should not worry about its fuel efficiency.
Big cars are meant for luxury, comfort, etc. and not fuel economy in particular.
If you are interested in a fuel efficient car, I would suggest to go for 660cc or 1000cc hatchback, not a 1800cc sedan.