The Buick isn't doing much for your E85 mpg. The problem with U.S. auto technology is the EPA requirements of having balanced chemical combustion. Meaning they utilize the oxygen sensor to drive the fuel use. This is a problem for ethanol that contains chemical oxygen. The chemical oxygen content of ethanol should be a valued attribute since oxygen is critical to efficient engine power generation and emissions of tailpipe. The EPA regulates upon a benchmark they learned from automotive powered by gasoline. They apply the same standards to high ethanol blends and when doing so they merely burn ethanol at the same chemical balance of gasoline. In other words they waste the fuel. What they should do, is to determine the lowest emissions. To allow automotive technology to maximize the ethanol fuel abilities and measure the actual tail pipe emissions. Europe does some of this. Ethanol likes to burn lean, generate high torque, and high combustion pressure. This would be the often phrase we hear of downsizing and and down speeding. I did read the department of energy has awarded R&D money to facilitate this generation of efficient engine development
Unfortunately, present day were stuck with buying and testing vehicles mpg to search for vehicles that handle ethanol more efficiently. If we find a true winner, it's probably a fluke that the EPA hasn't cracked down upon. It's funny, but old and basic auto's of yesteryear handed E85 better than modern highly computer controlled cars. My daughter had an '89 tempo that didn't change mileage with E85 hardly a bit. Also, the car would pass emission test without a hitch.