On Feb 15, 2:24 am, WingFlaps wrote:
Well if you know the complete history of a 2000 hour engine that never
had anything but plugs replaced then as I said, that's great. But if
such anecdotal evidence is what you base reliability figures on then
I, personally, would not have much faith in them. That's my point. I
really don't have any axe to grind on engine type but am trying to be
objective -if that's OK with you? The heavy use Lycoming engines I
have seen all seem to be well down on compression by 1200 hours and
that is not a good look for them to reach 2000 -but I have only a
sample of about a dozen. Of course we'll ignore the complete recall of
cylinders that took place recently... So, is 2000 hours service
normal?

As for being stuck on the idea that one engine type is superior it's
not me as I'm only trying to glean _facts_ and don't I own anything -
what about you? Right now I am looking at the diesel STC for Cessnas
so this is not trivial but a near $1M question.

We run six Lycomings in a flight school. They aren't
babied. They run, hard, their whole lives. Hot weather, cold weather
(down to -25°C), wet and dry. Off-airport strips some of the time,
with the usual dust and other airborne junk. They reach TBO no
problem, except for the one O-235. It has a problem with running too
cold, which leads to lots of condensation in the engine, enough that
corrosion of the front cylinders is a real hassle. The corrosion pits
cause fairly rapid wear of the cylinder wall, leaving a ridge at the
bottom of the ring travel over which the aluminum piston pin plugs
must ride. Those plugs start getting shaved and bright bits begin
appearing in the filter. Compression is still good at that point,
mid-70s or better. Compression doesn't say everything. Compression is
taken with the piston at TDC, above the corroded area. A five-ring
piston would stop that. So would bronze plugs. Neither are available
for that engine.
The other engines, three O-320s and an O-540, all reach TBO
with no hassles whatever. Engines that are run regularly and properly
maintained are no trouble. Using good oil (Aeroshell 15W50, which has
the Lycoming-recommended additive already in it) goes a long way
toward a long life. Cheaper oils are false economy. I can't remember
the last time we changed a cylinder on one of these engines. Another
good thing is to throw away the cheap screen-type oil filter and
install the spin-on adapter. The spin-on filter costs more, but does
it really? The screen stops only the bigger bits that might have part
numbers on them. The smaller bits that get through can score cylinders
and bearings. We have more trouble with leaky rocker cover gaskets on
Lycs than with anything else they make. The aftermarket silicone
gasket fixes that.
So, if you want the engine to last well, see that it's broken
in as per Lycoming's instructions. Exactly. Then change the oil when
it should be changed. Don't run it unless it will fly. Don't make a 20-
minute flight and then put it away. Get that oil hot. Use good oil.
Get the engine warmed up some before taking off in cold weather. If
possible, use some sort of winter fronts to reduce the cooling
airflow. Go easy on the throttle movement; don't slam it open. Keep
that carb heat closed when taxiing through dust. Learn how to lean it
so that it doesn't foul up.
The smaller Continentals have weaker cylinders. Usually need a
top overhaul halfway to TBO. Exhaust valves go easily. We had poor
service from the O-200s in the 150s years ago. Bigger Continentals are
more robust.

Dan