"Matt" wrote in message
. ..
Hi everyone. I was reading about Petersen's STC to use mogas in the
O-235. Apparently the STC for the O-235 only allows premium (91 octane) to
be used. I would still be reluctant to use premium since it is a "step
down" in octane for the O-235. I would not have a problem if I was flying
an O-200 and could "step up" to 87 octane since the engine was originally
certified to run on less.

Has anyone ever found premium available for aircraft use at an airport?
To tell the truth, I have never flown into an airport with mogas
available. The chance to cut down the cost of flying is appealing to me,
but not if it means the inconvenience of having to refuel from gas cans.

Matt

Matt,
I've got one of the STCs for my 152 and used to use mogas (91) very
frequently. The O235 ran perfectly on it and I put well over 1000 hours on
my previous engine using mogas 90% of the time. (a tank of 100LL once in a
while as the STC recommends).

I put in a factory OH engine about 6 years ago and although I've paid and
transferred the STC to the new engine, I have not used it for two reasons.

First, the factory warranty is void if used during the warranty period.

Second, most if not all mogas in my area now contains some alcohol, which is
not acceptable.

Yes I had to refuel from gas cans, and a careful grounding scheme should be
used along with conductive fuel handling equipment. It was a hassle. I
have never found premium gas at an airport.

The O235 in your 152 is really a medium compression engine and the 91 octane
(R+M)/2 is just fine. The lack of lead in the gas is very good for the Lyc
O235 which tends to foul the lower plugs with lead deposits, even with
aggressive leaning. Just use some 100LL on occasion to keep the valves
happy.

John Severyn