Fuel class 8 is not a specific type of fuel. Class 8 refers to the grade level in which students learn about fuels and their properties. Fuels are substances that produce heat and light energy on burning, and examples include wood, coal, cow dung cakes, kerosene, LPG, petrol, diesel, and biogas. An ideal fuel should have a high calorific value, burn without giving out any harmful gases, not be more valuable for some other purpose than a fuel, be cheap and easily available, and be easy to handle, safe to transport, and convenient to store.