E85 Checker - FOR E85 FUEL ONLY; Calibrating the right air/fuel mixture is important to gain proper power and efficiency from your carburetor and engine. But for vehicles running E85 fuel, proper calibration is difficult if you don't know the exact percentage of ethanol-to-gasoline in the fuel. Because E85 fuel can vary in the amount of ethanol and gasoline mixture, Holley's E85 Checker is an essential tool that can instantly determine the ratio in the E85 fuel you're using. Holley's E85 Checker fits in your pocket or tool box, and is easy to use.