What is UL 91?

UL 91 is a common term often used in the context of aviation fuel. It refers to an aviation gasoline with a minimum octane rating of 91, which makes it suitable for use in piston-engine aircraft.

The Technical Specifications

In order to be classified as UL 91, an aviation gasoline must meet certain technical specifications. These specifications include a minimum Motor Octane Number (MON) of 91 and a Research Octane Number (RON) of 96. The MON indicates how well the fuel resists knocking during the actual operation of an engine, while the RON measures its knock resistance under controlled laboratory conditions. By meeting these stringent requirements, UL 91 ensures optimal performance and safety for aircraft engines.

Advantages and Benefits of UL 91

1. Enhanced Performance: UL 91 is specifically designed to enhance the performance of piston-engine aircraft. Its high octane rating ensures smooth and efficient combustion, leading to improved engine power and overall performance.

2. Increased Safety: Aviation fuels with lower octane ratings are more prone to detonation or knocking. These issues can cause engine damage and result in increased maintenance costs. With its higher octane rating, UL 91 significantly reduces the risk of engine knocking, ensuring safer and more reliable flights.

3. Environmental Compatibility: UL 91 is formulated to minimize environmental impact. It contains lower levels of lead compared to other aviation fuels, making it more eco-friendly. Additionally, UL 91 has a lower vapor pressure, reducing the chances of evaporation and associated harmful emissions.

Usage and Availability

UL 91 is commonly used in smaller piston-engine aircraft, including private planes and some helicopters. It provides a cost-effective alternative to other aviation fuels while still maintaining high performance and safety standards. However, it's important to note that not all aircraft engines are compatible with UL 91. Pilots and operators should always refer to the aircraft's operating manual or consult with maintenance professionals regarding fuel compatibility.

In terms of availability, UL 91 may not be as widespread as lower octane aviation fuels. It is important for pilots to plan their refueling stops accordingly to ensure the availability of UL 91 at their desired airports or FBOs (Fixed Base Operators).

Overall, UL 91 plays a crucial role in the aviation industry by providing a specialized fuel option for piston-engine aircraft. Its high octane rating, accompanied by various advantages and benefits, makes it a preferred choice for pilots looking for optimal performance and safety.