If the "bunny huggers" are right then using less fuel may allow us to reduce the impact of global warming and if they are wrong then it will mean that the fuel lasts longer.
Also we might as well reduce the amount of fuel we use for 2 good reasons:
1) it costs so much
2) if there is a global climatic catastrophe then the bunny huggers will be unbearable with their "I told you so".
- I can't see a bunny to hug so the cat will have to do for now.