There to now with avgas? Following a flurry of activity at EAA AirVenture-briefings and meetings, mainly-has the flag inched forward toward a replacement for 100LL? In short, its hard to tell. If there’s substantive progress, its occurring behind closed doors, although the venue has changed. By early September, the FAA revealed a generally positive test result on a 150- hour test cell run with Swifts UL102 fuel, a variant tof several blends it has developed. Meanwhile, General Aviation Modifications Inc. still has before the FAA a request to approve its G100UL via STC. From what were able to surmise, this effort is stalled, but GAMI says its still pursuing it. Both Swift and GAMI have applied for ASTM International approval of their fuels, which the FAA insists upon before certifying any fuel for general use. Its at this point that things gets complicated, muddied by flyspeck technical considerations that may or may not matter and by politics. Were told that three potential test fuels may go before the ASTM fuels committee in December: Swifts blend, GAMIs G100 and a proposed new fuel called 100ULL (ULL for ultra low lead). The ultra low lead idea percolated up from the GA industry and doesnt have a named sponsor yet. Depending on how the fuel is formulated, it could contain as little as half the tetraethyl lead used in 100LL. The hope is that such a fuel might provide at least an interim step to satisfy proposed EPA rules for reduced emissions, which is whats driving the coming extinction of 100LL. But there are two big unknowns with 100ULL. Will it provide the necessary knock resistance and will EPA go along with an interim lead reduction until it can be eliminated? With no direct sponsor, its also unclear how 100ULL would be tested. In late July in a letter to AOPA at the associations request, EPAs Margo Tsirigotis Oge said the EPA currently had no timeline for lead regulation and that its advanced notice of proposed rulemaking doesnt propose to ban leaded fuels. Nor, she said, does the EPA have the statutory authority to ban lead in fuels. The next day at AirVenture, FAA Administrator Randy Babbitt said exactly the opposite in carefully parsed words that said that only EPA had the statutory authority to regulate lead emissions. (In this context, fuel is merely the vector for the lead.) 
