I have been a loyal customer with IOC since about 7-8 Yrs... Have a IOC Pump near my home and they are pretty decent. Have been filling my Figo with Normal Diesel always there, and never have had any issues yet.
Tried BP once and HP couple of times. And Shell for Diesel??? What I would prefer is COCO Pumps, which is not in vicinity.
Behind the screens... I have Credit Card tied up with IOC... Which benefits me with Turbo Points .
Nearest bunk is Reliance (COCO) so I fill petrol from there most of the time. No issues - both quality and quantity are assured. Recently, Reliance petrol price has been brought at par with PSU bunks but earlier I had to pay more than PSU bunks.
I was regularly switching betweel HP,IOC and BP. But now for the last 3 fills in my Maruti Alto, I am filling Shell Super Unleaded. Mileage hovering around 12-13 in city for now. But they mileage improves as we stick to it regularly. Filling in the same bunk with the same nozzle. The Super unleaded is retailing around 81.40 rupees in the Ambattur Shell Bunk in Chennai.