The nation's largest oil firm Indian Oil Corporation today flagged off a "check and fill campaign" in a bid to make customers aware of quality and quantity of petrol available in its retail outlets.

"The check by the customers would comprise basic facilities like filter paper check for petrol, five litre measure and density check. Customer can give the feedback to the toll free number at 1800-2333-555", a company release here said.

The three-month campaign was formally inaugurated by state civil supplies commissioner K Rajaraman.