Isn't the commonly available Avgas low lead (in comparison to conventional high lead Avgas) rather than unleaded?
There is supposed to be unleaded Avgas available but I have know idea how available or how much.
AVGAS 91/96 UL is increasingly available, typically 10 to 15p a litre cheaper than 100LL. The nearest airfields to me that stock it are Compton Abbas and Popham.
Good stuff. I've had people insist to me that 100LL was unleaded which was simply not true but it's a long time since I've tried to get any sort of Avgas for anything.
AVGAS LL has 0.56g/L tetra ethyl lead. The old 100/130 AVGAS had 1/12 g/L. Each gram of TEL has 0.6 g of free lead in it, most of which goes out in the exhaust. So a 85L tank fill of 100LL in the DH Tiger Moth will have 50g actual lead in it.
Another important point is that AVGAS has no alcohol added, no oxygenates and has a much tighter volatility specification to prevent fuel vapour locks.
Increasingly engines are being certified to use MOGAS, (Standard Motor Fuel) but it is on an individual aircraft installation basis because of the fuel vapour lock issue. In some cases the fuel system requires substantial modification.
