l own a Getz 1.3Lt and sorry not Santro, which is 2 months old and done just 500Km. The problem is that the car does not wanna pull from 40Kph in 4th gear, with just 3 people and the A/C on. l have to down shift to pick up speed. Please suggest.

That is normal when you consider 1st gear alone will do 50km/h. Do not be afraid to rev the engine, at 40k is you should be in 2nd or 3rd gear, no way 4th. It is a small engine so the torque is limited, + labouring the engine is bad for your clutch and engine and also returns worse fuel economy. l would be shifting at around 3-3.5k rpms.