Lycoming says 12 years or 2000 hours, whichever comes first. However,
many airplanes exceed these "limits" under certain conditions. Flight
schools regularly exceed 2000 hours because their engines are flown so
frequently they avoid internal corrosion which is the main killer of air
cooled engines in airplanes. So, if flying MORE frequently makes the
engine last longer, guess what flying LESS frequently does???

Exactly.

One poster responded that the engine was probably rusted up internally.
Others said that this conclusion was "defective" (I am using polite
language). Their opinions, your money. Others also balked about pulling
a jug for a prebuy. Normally, it is true that this is not done. There
are plenty of uninformed buyers with enough credit to buy a bird
uninspected and sight unseen. So, an unusual request like pulling a jug
will no doubt get you a firm "No F^@%!*G Way" of some kind of robust
belly laugh.

It is still your money. If you want to price the thing as a runout and
deduct the full overhaul value (along with any other firewall forward
item likely to be worn out - like everything) from the price and make an
offer, go right ahead. I would. However, it is likely the owner will
pass on such an offer and sell the plane to a less informed buyer,
probably for full price.

The reason many owners will tell you the engine is perfectly fine is
because they have an old overhaul themselves and are in denial. Some
have glowing anecdotes about old overhauls that are "running fine". I
have never seen anyone follow up with the report that the "fine" engine
self destructed some time after they weighed in with their opinion. If
you are curious, call up the engine shops and ask what they are seeing
for this particular engine/bird combination. Might be a good piece of info.

Compressions are ONE of the signs. Calendar time since overhaul, hours
since overhaul, oil analysis, oil CONSUMPTION, climate, frequency of
hours flown, type of use (training, long x-country, pipeline survey,
etc) are all contributing factors.

Good luck,
Mike

wrote:
Hey Guys,

I'm looking at at 172 that has 1100 hours since overhaul, holding 73/90
++ on all cylinders...the only thing holding me back, last overhaul was
1976...

I've talked to several seasoned pilots / aircraft owners that say as
long as it's holding good compressions, don't sweat it....

Any opinions?

Thanks,

Jamie A. Landers
PP-ASEL
Looking for a 172