What ethanol content is modern small engine fuel delivery systems calibrated for?

Modern small engine fuel delivery systems are primarily calibrated for E10, which is a fuel mixture consisting of 10% ethanol and 90% gasoline. This particular blend has become the standard for a variety of small engines, including those found in lawnmowers, chainsaws, and other power equipment.

The choice of E10 as the standard is due to its compatibility with most engine components and fuel systems, allowing for optimal performance without causing significant damage or maintenance issues. E10 offers a balance between being environmentally friendly through reduced emissions while still providing sufficient energy content for the engine's operation.

Higher ethanol blends, such as E15, E30, and E85, contain greater proportions of ethanol and can potentially lead to problems in small engines that are not designed to handle such concentrations. These complications may include fuel system corrosion, starting difficulties, and diminished performance, as well as increased risks of vapor lock in some conditions.

Therefore, the calibration of small engine fuel delivery systems for E10 ensures that they can reliably operate with widely available fuel while minimizing risks associated with higher ethanol content.