There are only two options that would meet your requirements of a diesel automatic and under Rs 13 lakhs. These are the Mahindra XUV 3XO and the Tata Nexon. It would be nice to know a bit more about your requirements to pinpoint one.
The Tata Nexon is a good option, as fuel efficiency is very important for you, as its efficiency is higher than the 3XO. In our real-world tests, we got an average of 18kpl for the Nexon and 15.5kpl for the Mahindra.
If, however, driving pleasure and interior space are important, then you would be better off in the 3XO. The engine is refined and delivers good performance. Also, the car is spacious from inside, especially at the rear, where you will find more passenger room than in the Nexon.