> The new replacement fuels are good, but they have one general large drawback. They require a recertification of the engine/frame of the plane. According to th

> The new replacement fuels are good, but they have one general large drawback. They require a recertification of the engine/frame of the plane. According to the lobby group AOPA, it will cost the industry in excess of $150 billion annually in the US alone. Also (at least in the UK), UL91 (the unleaded-alternative for some aeroplanes) is more expensive than 100LL. E.g. looking at a nearby (GA) airport, the price for 100LL is £2.22/litre and UL91 is £2.60. You can sometimes use Mogas (literally automotive unleaded) but this has some temperature restrictions due to the vapour point.