Where I live there is no biodiesel available, I wish it was. Buying a new car is also not an option available for a lot of people.
There are quite a few different things available now to purchase that allow you to make your vehicle more less hard on fuel.
Do they work? I haven't tried them, so I can't say.
So I am going to stick to trying to conserve my fuel usage as much as possible.
Here is what i try to do. It very much just common sense, but sometimes we need to be reminded of those things to make us more aware of them.