California drivers fed up with painfully high gas prices may be tempted by E85 ethanol fuel. The fuel is running for about $2.69 a gallon, which is roughly half the price of regular unleaded. However, there is a major catch: That bargain price is not meant for most vehicles on the road. Here's what to know Made with a high percentage of ethanol and a smaller amount of gasoline, E85 is not a universal substitute for regular fuel. Only flex-fuel …