It's the users who dump oil, AND don't use alternate transportation like the bicycle, or train, or walking often enough. We are the real problem. The engine has very little modification, but the vegetable oil has to be chemically changed a little. Unfortunately I don't think it will solve your problems. European Union have to get rid of it.
Cheap land promotes sprawl.
No land use controls allows the cheap land to be sold. People move out there and demand streets and traffic signals and wider streets, etc. This is the American way since day 1. It is the reason California is here. Transportation allows sprawl.