With an experimental, you don't need an STC. You can run the engine on
whatever makes you happy... That said, look at the compression ratio for
the engine you're considering. Lower compression = happier with autogas. I
believe some engines with 8.5:1 compression can be STC'd on autogas, and
should be relatively happy with it, but 8.5:1 is right at the limit. A lower
compression engine would be happier with autogas.

Auto gas has higher vapor pressure than avgas, so vapor lock is something
you really need to consider. At high altitude on a warm day, the engine
might just decide to quit... Or on a day when you flew, then made a quick
turn-around, the engine compartment might be warm enough to cause a vapor
lock problem. Then, there is the problem of accidentally buying winter
formulation autogas (with a higher vapor pressure) during a warm spell...

Here's a link to the best info you're likely to find on autogas and STC's:

http://www.eaa.org/education/fuel/autogas_vs_avgas.pdf


"John Skorczewski" wrote in message
om...
I appreciate the info--- but I still have questions. Say, I wanted to
built an RV-10 with a 260 lycoming engine. How do I find out if it can
be stc-ed for autogas??? ---and if not what is the biggest lycoming
engine that can burn autogas? Who has info like this??