What happens to octane rating during phase separation?

During phase separation, the octane rating of fuel is impacted because the process involves the separation of ethanol from gasoline when water enters the fuel mixture. Ethanol has a higher octane rating compared to regular gasoline, and when the ethanol separates out due to the water contamination, the remaining gasoline's octane rating is lowered.

This decrease in octane rating can typically result in a drop by two to three points, which can affect engine performance, potentially leading to knocking or pinging. The phenomenon of phase separation not only alters the chemical composition of the fuel but also compromises its quality and effectiveness in combustion engines.

Understanding this impact is crucial for anyone working with small engines, as it emphasizes the importance of maintaining fuel integrity and being aware of how fuel can degrade when exposed to moisture.