I can say that the engine assembly is different for flex fuel versus straight gas. I worked in the Toyota engine plant that builds the V6's for Camry, Avalon, Sienna and RX. The short block and heads were the same but all of the associated rubber lines used for fuel were changed over to stainless steel. All of the seals in the injector system, as well as the injectors, were completely different than for a straight gas engine. The Government, EPA or whoever, saying that E15+ is fine for all vehicles manufactured after a particular date kills me. They aren't set for the higher alcohol content. It also ticks me off that we are still paying the same price for "gas" when we're only get 85-90% of what we're paying for. Not to mention that the increased ethanol production based on corn is driving up food prices. If it was being made from some non-food based source it would be different. We're really paying for it two or three times, once at the pump, once in the government subsidies and again at the grocery story. I don't have a problem with alternate fuels but they should be able to stand on there own in the market place in my opinion.