Flex fuel vehicles have been around for quite a while now. There are nearly 20 million vehicles on U.S. roadways that can run on E85 or are classified as flexible fuel vehicles, making the U.S. the second largest ethanol market outside of Brazil. That's quite a large quantity considering that only 35% of owners are even aware of their vehicle’s capability, and far fewer than a million are regularly filled with E85. Since you're here on the Advanced Fuel Dynamics site and have an interest in our PROFLEX Commander performance flex fuel system, you probably already understand the benefits that E85 brings to the table: more horsepower, better torque, cooler operating temperatures, lower emissions, and a lower price per gallon. It's a far better fuel for performance than gasoline by nearly every metric. Why then, if so many vehicles can use it, do manufacturers not proclaim it from the mountaintops? The answer, as it usually is, lies in a loophole in regulations. The Corporate Average Fuel Economy (CAFE) regulations were enacted by Congress in 1975 and were intended to improve the average fuel efficiency of automobiles over the subsequent decades. One provision of the requirements granted a fuel economy credit for every vehicle sold that ran on an alternative fuel, like E85. This meant that a flex fuel vehicle that averaged 25mpg on gasoline alone would be rated closer to 40mpg when E85 was factored in, thus meeting the higher standard. On paper, this sounds like a great way to incentivize development of alternative fuel technologies and reduce American reliance on foreign oil. But in practice most auto manufacturers simply installed flex fuel capability as a sort of retrofit to their existing vehicle systems, focusing on high volume vehicles that also tended to have worse mileage, like pickup trucks. Sure, these vehicles can burn E85, but not very well, and they certainly don't get any of the performance benefits out of it like we can with the PROFLEX Commander E85 Flex Fuel kit. Most vehicles that are advertised as "flex fuel capable" don't actually monitor what type of fuel is being burned. Instead, these types of engine management systems guess as to the type of fuel by reacting to the feedback coming from the rear O2 sensors. The typical function of an oxygen sensor is to monitor the fuel and air mixture within the cylinder to ensure it isn’t rich or lean and have the computer make adjustments as needed. Since E85 requires a larger volume than gasoline for a stoichiometric mixture, the ECU makes a short-term adjustment for what seems like a lean condition. If the adjustments continue for a long enough period of time, the ECU assumes that you're running E85 and switches the fuel map. Because this type of reactionary flex fuel system only functions over the long term it's easy to see how it can cause problems when you switch between the two fuels. You'll often end up with a vehicle that runs very poorly on gasoline after running a tank of E85 and vice versa. It's also generally advised to drive easy on the first tank after you go from one to the other, so you can avoid damage to the engine until the system can adjust. Even then, there's little provision for blends of the two which can be a big problem if your tank is running low and there's no E85 available. The PROFLEX Commander system is different and doesn't guess when determining what the ethanol content of your fuel is. Instead, it's monitored in real time and adjustments are made in with nano-second fidelity for seamless performance. It won't matter if you have a full tank of E85 or a 50/50 mix with pump gasoline, with the PROFLEX Commander your car will make the maximum level of safe and reliable power on any fuel blend. Cars are meant to be driven, so fill up and go!