Swift UL94 and UND

The University of North Dakota had been using Swift UL94 unleaded avgas until they experienced valve seat recession in their fleet of trainers.  They have since returned to using 100LL.

Lycoming has indicated they think the problem is due to the aromatic content of the fuel, and fuel leaning procedures.  Swift rejects aromatic content as the cause, and has recently acknowledged leaning procedures may have something to do with it.

Petersen Aviation is of the opinion that this problem is primarily due to leaning procedures. UND operated at peak.  Engine damage can occur when using unleaded fuels while operating at peak or lean of peak. Therefore, we reiterate our recommendation that you operate rich of peak and avoid running at peak or lean of peak unless you are using 100LL.  In this case, you may follow the standard leaning procedures for your airplane. However, when using unleaded autofuel or unleaded avgas, operate rich of peak.

Please contact us if you have any questions