In Islamabad my 1.6 auto sunroof gives 10.5 in city and 15+ on motorway. As rare said that parts are Genuine Mitsubishi, Japanese, Chinese/Taiwanese, and also kabali. Personally, I always recommend genuine parts. They cost more but last a long time so you get peace of mind. Maintenance costs of the car depend on the care taken by the previous owner. Most cars being sold have been driven more than 100,000km and require a quite a bit of small/medium work to make them good as new. Since people aren't eager to spend that money they go for selling the car. Oil filter is for 750, air filter is for 3,000.
By engine head costs I am not sure what you mean.
Market value of the car is lower as compared to civic and corolla (but it also means you'll be able to get one cheaper). Resale of wornout old lancers is low and slow but if there's a well maintained car I've seen it get sold within 4 days!!