on my last fill up, i went to the service area to get the cabin ac filter and the engine air filter, cleaned with compressed air. the guy (aka choTa) suggested that i should get the AC grill (evaporator) cleaned as well, there were a lot of insects and dust stuck into it, he cleaned it with surf and pressurized water. some water went into engine bay as well, and then he deliberately sprayed some more water on the engine to clean it, i was curious and asked him that it may damage the engine or something, but he said, "sir jee, inhain kuch nahin hota" (he meant these newer engines are not damaged by water) and allah ka shukar hai, nothing happened.
other outcomes of the visit,
-i got 11km/l fuel average
-tyre pressure was a bit low, so that could also be a reason for bad fuel average, i got them inflated to 33psi, slightly above the recommended pressure, but i think its safe and would give lil better mileage
-ac's cooling got better (i believe, although prolly there is no way i can measure it to be certain)
-ac's throw also got better, now i use it the first dot of the knob, before that i used it at second dot.