We should conserve the fuel, because the fuels are getting depleted, and the chance for the fuel in the future will be less.
Then, the future generations will suffer, with the lack of fuel.
If we didn't conserve the fuels, then, there won't be any re-accomplishment.
So, it is important to conserve it, as it takes millions of years for it's formation. So, the Sustainable development is essential, and the conservation of the fuel is essential.