I have faced such issue with my previous car Honda City with 160k on odo. Problem was more severe than yours because car started getting over heated at speed of 90 km/h with AC. I consulted many mechanics to fix this issue. All said that "Engine bnwana parey ga" because they could earn good amount of money after making engine.
Do not trust such type of fraudiyas.
WHAT I DID TO FIX THIS ISSUE?
I simply cleaned the radiator with pressure water (same used for car service and cleaning) and issue was fixed permanently. I sold that car with 210k on odo without any issue of engine.
REASON OF PROBLEM:
When large amount of mud is stucked in blades of radiator. Radiator is not able to transfer much engine heat to atmosphere.