There are not many petrol automatic cars, at any price point, that would do upwards of 15kpl these days. Turbocharged cars, especially, require extremely careful driving to achieve high fuel efficiency numbers, and the automatic gearbox reduces these chances, as the gear shifts are not in your control. If fuel efficiency is your ultimate concern, we would recommend a good naturally aspirated petrol engine, in a small, relatively light car. The Maruti Suzuki Fronx 1.2 petrol AMT is a good option, but its automated manual gearbox is not very smooth, and its engine is not very powerful. As a trade-off, you could also try the Maruti Suzuki Brezza 1.5 petrol AT, which has more power and a smoother torque converter automatic. But will deliver slightly lower - but still very good - fuel economy.

It is very sad that you're having to retire your well-maintained Polo due to the 15-year rule in Delhi NCR. Since you have a budget of Rs 7 lakhs, we'd advise you to get a 2020-21 Maruti Brezza or Toyota Urban Cruiser, both of which are smooth, well-built cars. Their seating position is high, visibility is good, and controls are light, which makes them very user-friendly. 

Also, try finding the newest possible example, which will ensure that you drive the vehicle for 9 or 10 years before it reaches the 15-year age-limit.

For your outgoing car, you could consider getting in touch with used-car platforms such as Spinny; they'll do the paperwork, and should get you a good price.

Given your requirements, you should consider the Maruti Suzuki Brezza. The Brezza has a comfortable and spacious cabin that can easily accommodate four adults. It also comes with a refined 103hp, 1.5-litre petrol engine paired to a smooth 6-speed torque converter automatic gearbox. 

Maruti claims the Brezza automatic will do 19.8kpl. The Brezza is also relatively easy to drive, and being a Maruti product, it will also be stress-free to maintain. Maruti Brezza price for petrol-auto range starts from Rs 10.60 lakh to Rs 12.86 lakh (ex-showroom, India). 

The ideal car for your requirement is the Maruti Suzuki Brezza. Thanks to its wide rear seat, five adults can sit in good comfort, and the ride quality is comfortable enough even for long journeys. It is a proven product and, being a Maruti Suzuki, you can expect low maintenance costs and reliable ownership.

There are, however, two caveats. The Brezza facelift is expected very soon, so it may make sense to wait if you are not in a hurry. Also, the current generation of the Brezza has not been crash tested yet, while the previous generation was tested by Global NCAP and had scored a four star rating.

If you want to buy a car immediately, the Mahindra 3XO is another strong option. It comes with a more powerful turbo petrol engine that delivers effortless performance even with a full load. Its wider body makes it one of the best five seater options in the segment. It has also scored a full five star rating in the Bharat NCAP crash tests.

Within your budget, you can opt for the REVX A variant of the 3XO or the ZXi variant of the Brezza.