Take a look at the Toyota Echo and Golf Turbo Diesel. Two mass produced cars that provides excellent mileage, even compared to hybrids. And developed without massive R&D support from government. Image what we can do if we take a serious attempt at increasing efficiency of oil burning engines. Unfortunately, we haven't and it doesn't look like we will in the short term.Serveral things are working against efficiency improves in oil burning cars. It's not sexy like alternative fuel. People like to have more power under the hood than they need. People like their cars to be big and heavy.