WOW!.... explosions in GTAIV are great. Its a bit hard to make a car explode by just collision. Unlike its ancestor san andreas, GTAIV's cars are more realistic as the car even as an engine blowout scenario which makes it harder for explosion. But just remember to shoot near the petrol tank. Unlike san andreas the petrol tank is not marked. just aim it somewhere on top of the rear wheel. around 10-20 bullets must do the trick.
