The present invention provides an unleaded, piston engine fuel formulation comprising a blend of mesitylene, pseudocumene and isopentane having a MON of at least 94 and an RVP of 38 to 49 kPa at 37.8° C. In certain aspects, the formulation comprises specific weight percentages of each of the mesitylene, pseudocumene and isopentane components, and varying MON ratings. In additional aspects, the formulations comprise a combination of mesitylene, isopentane, and one or more additional components selected from the group consisting of pseudocumene, toluene and xylenes. In certain embodiments, the formulations also include alkylates and or alkanes. The formulations have unusually high MON ratings, and desirable RVP and distillation curve characteristics for formulations not including additional components, particularly octane boosters.