MAINTAIN YOUR VEHICLE
Not only are you extending the life of your vehicle, but you are creating less pollution and saving gas. A properly maintained vehicle, clean air filters, and inflated tires can greatly improve your vehicle's performance. And it might not hurt to clean out the trunk—all that extra weight could be costing you at the pump.
Source: 50 Ways to Help the Planet
In my case, it's my bike that I maintain. A good tune up at least once maybe twice a year will help your bicycle last longer. If everyone took better care of their more expensive items then they wouldn't needs as much replacing as often.