What is an ideal fuel?

before choosing a good fuel we should check that:

1. the fuel should be inexpensive

2. the fuel should be easily available.

3. it should have a high calorific value.

4. it should have a low ignition temperature but not lower than the room temperature.

5. it should neither burn too fast and nor too slow.

6. no residues should be left on combustion

7. it should be safe to store, handle and transport.