Based on several of the comments on this subject, some guys are missing
the point of Jeff Scot's account of his gas problems. It wasn't the
ethanol that damaged his fuel system components, it was something else .
. . some additive(s).
Jeff York makes the point that such extensive damage had to have started
at some point prior to Jeff Scott's arrival in Arkansas. Since Jeff has
been using his mogas/avgas mixture for many years in Los Alamos without
problems, a mystery still lies at the bottom of this situation if the
information Jeff York provided is accurate - that is, if the damage was
cumulative, starting well before Jeff Scot left Los Alamos. I don't
think so. Jeff would have noticed it.
Reading the situation as it happened, Jeff Scot's fuel rig on his truck,
along with the damage to tanks and tank fittings on the Cub, all happened
abruptly. I would conclude it was a result of gas bought in Arkansas
with some new and strange additive that is aggressively corrosive. So
far it seems there's been no damage to Jeff's KR, with the same fuel.
This could be that it just hasn't had time to do it's nasty work - or
that the fuel tank and components in his KR are resistant to this
particular mysterious additive blended into Arkansas fuel. I'd not be
surprised to learn that Jeff has drained and flushed his fuel system on
the KR.
Jeff Scot makes the point that the lead in 100LL can cause deposits on
valve stems thus causing premature wear to the guides. When I had my
heads off of the GP2180, I had slight discoloration on the valve stems
closest to the face. There was discoloration (a light film that came
right off) also within the valve guides near the face. I threw the
valves away, however I have a picture of an old valve together with a new
valve and I'll attach it to this post. You'll see no accumulation of
lead on the old valve. I didn't clean it up. I did clean the guides
with a narrow stiff brush and they not only looked new once I'd done
this, there was no play in the guide when inserting the new valve stem.
In other words, I didn't have any lead build up. I had no idea 100LL had
half a gram of lead in every liter. That's a hell of a lot of lead.
Running lean as I do, the lead has not caused a problem with my guides
despite the very high lead content of the fuel. With that much lead in
the fuel, I think next time I have the engine apart I'll bump the
compression ratio up from 8 to maybe 11 or 12 :-) Might as well take
advantage of such great anti-detonation protection.
Jeff Scot does not agree with the idea that lead acts as a lubricant as
some old timers say. I tended to agree with that idea - that lead is
slippery and protective. I tend now to believe what Jeff has told me
about lead since he knows what he's talking about as opposed to the
opinions of old timers at the hangar who base their opinions on
experience and rumor and the collective wisdom of the mob and, by no
means, in any case, is everyone in agreement. As it happened, my engine
had suffered no accumulations of lead and the guides looked amazingly new
after 500 hours, showing no wear. None. The reason for that was due to
using elephant feet on the rocker arms and because I run the engine very
lean at full throttle, except for takeoff and climb and, in the winter, I
even lean it in the climb.
Anyway, all I started this out to say was Jeff's problem has nothing to
do with octane. It has to do with something strange in the mogas in
Arkansas and wherever else this mysterious substance is blended into the
car gas.
I'll put whatever Chevron Supreme I have at the hangar in my car and even
though my use of mogas has been slight, I won't be using it at all in my
VW - even though the VW is originally a car engine. I have a primer, two
fuel pumps, fuel valves, fuel lines, fuel filters, an Ellison carb, a
fuel pressure gauge, hoses connecting all this, etc. I've never had a
problem with any of these components using avgas so I'll continue to do
so. I don't think they blend additives with avgas. Aviation engine
manufacturers design their engines based upon the use of a fuel that
doesn't bounce around with different blends compensating for the seasons.
Plus, I seem to get more power out of the engine with avgas. It might
be my imagination, but probably not. When I'm in the midwest buying gas
for the car at those stations that sell only gas with ethanol, my mileage
drops. There is less energy in gas with ethanol than in gas without it.
I think it's just a matter of degree when it comes to ethanol in car gas.
Premium gas probably has less ethanol than lower grades, but I suspect
all gas has ethanol in it these days. I think it's something mandated by
Congress to subsidize the farmers who produce it. The Chevron guy told
me that on the phone if I'm remembering correctly.
Mike
KSEE
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