I can bet that these mileage related problems of GD110 is because of bad fuel coming these days. Heck a few Fuel Station owners accepted it on my face that Hi-Octane coming these days is exactly like the normal Petrol was a few months ago. Bad quality fuel means, more consumption, which means more sale for the company. In the end, "WE" the consumers are the ones get squashed by these acts.
Coming to the GD110 ... i asked a few owners to use only Hi-Octane in it, and report back the mileage readings. None of them responded. I am still fairly certain that if you guys use Hi-Octane, mileage can be increase considerably. (However, i am not sure if you guys will like the Cost per Kilometer, because that'd still be higher than the normal petrol).