[codexb]

The problem is that they won't approve engines for general aviation that use unleaded gas. All the engines used in general aviation are basically 60 year old designs. General aviation is not a major concern for the FAA. It's an afterthought. And so they don't devote any time to approving new, modern engines and make it as difficult as possible.

[phkahler]

>> The problem is that they won't approve engines for general aviation that use unleaded gas.

Except that they did approve a lead-free fuel for use in all those engines last year. Banning leaded fuel is the obvious next step.

[jabl]

Many, or even most, of the engines are indeed old designs. But e.g. Rotax offers certified version of some of its 900 series engines, which are a relatively new design, some with fuel injection, FADEC, etc.