Oil is getting more costly to find and extract. But vegetable oil is renewable, recyclable, and cheaper than gasoline, and diesels were designed to run on it. A million restaurants pay to have used oil taken away; a million filling stations should get in line to start filtering and reusing that oil at half the price of gas.
Diesel engines are already more economical than gasoline engines, and the new ones are quiet and better for the environment than deep drilling and fracking. A simple conversion is all that's needed to get them running on veggie oil.
If a few individuals are currently willing to filter their own veggie oil to run their cars and trucks, how many more would get the conversions if they could drive up to a nearby station and get it at the pump for half price?