Devout Hindus light diyas not only during Diwali, but also during the other days of the year. If you want to light plenty of diyas, why not light them with oil that is environmentally friendly?
Method: Mix 2 litres of Palm oil, 1-2 litres of til oil, ½ litre mustard oil, ¼ litre coconut oil and 150 gms ghee. Heat this mixture on a slow flame. After the mixture is slightly heated, add neem leaves, (one bunch available in flower shops for Rs.10/-), Curry leaves (one bunch available in vegetable shops for Rs.5/-) and Tulsi leaves (one bunch available in flower shops for Rs.5/-). Continue heating on a slow flame and let the mixture boil, which will take some time since it is on a slow flame. Shut off the flame and cool the oil to room temperature. Pour it into a suitable container to store. You may use this oil to light 4-5 diyas every day.
Benefits: This oil does not cause pollution and at the same time gets rid of fruit flies, house flies and mosquitoes. People have a tendency to tell you to stop growing plants because according to them plants cause the growth of mosquitoes. Already man has been on a rampage cutting down trees, which are the vital source of oxygen for us. Instead of telling people, who grow plants to stop growing them, it would be better to light these diyas, which are good to the environment, particularly in places where there are house gardens and terrace gardens. You can light 4-5 diyas around 5.30-6.00 PM and repel flies and mosquitoes.
But if you have to light diyas for prayer/pooja, any oil other than palm oil can be used.