True, with the camshaft up high in the case it tends to “dry out” faster, which just makes it more prone to corrosion.
Then there’s the fact that camshafts are not always replaced at overhaul, so it could easily have far more hours than the TSMOH.
That said, corrosion protection oil additives have been mandated by Lycoming for many years and the AeroShell PLus products have them, Total does not.
I’ve known c152 doing 400 hours a year on aeroshell to eat camshafts.
Could it be due to a standard practice in the rental scene: renters starting up and taxiing like crazy under high power, with the engine still cold, across grass (high power needed) and taking off quickly after starting to move because they are being billed brakes-off to brakes-on? I see that where I am based all the time and even some of the instructors do it. It makes me cringe…
Normally, school owned engines make TBO easily.
Normally, school owned engines make TBO easily.
That’s news to me, even tough we bill true flight time only (there’s a pressure differential operated switch on the pitot and static lines and a counter).
Out of 4 new 172SP, one had a total alternator failure after ~300h, where I have no idea how mismanagement by a renter could have caused that. Plus all sorts of premature problems where it theoretically could be due to engine mismanagement.
Well, an alternator is an accessory, and has nothing to do with the engine management.
Could it be due to a standard practice in the rental scene: renters starting up and taxiing like crazy under high power, with the engine still cold, across grass (high power needed) and taking off quickly after starting to move because they are being billed brakes-off to brakes-on? I see that where I am based all the time and even some of the instructors do it. It makes me cringe…
I am not exactly an expert, but as far as I understand, none of this would have any effect on the longivity of the camshaft. In fact, i think there is very little the pilot can do that affects the life of the camshaft.
The problem is that, from info posted, we know nothing, zero, zilch, nowt of the usage pattern. Or the history before the school bought it.
Where I am based, Shoreham EGKA, loads of the planes parked outdoors (most school planes are) hardly ever fly in the autumn/winter. The months Oct-Dec especially are often low cloud and drizzle. No chance of any solo flying, not even rental post-PPL. Might do a few circuits with an instructor. During my PPL, 2000/2001, such a C152 would have seen maybe 5-10hrs in those 3 months. That is a prob99 heavy case of internal corrosion. Then somebody starts it up and revs it up, and we know the camshaft / cam follower interface is a very weak point in Lycos.
In fact, i think there is very little the pilot can do that affects the life of the camshaft.
Probably just regular flying, and using Camguard (which 99% of schools won’t do because it costs 25 quid per service).
I have recently seen some very interesting metallurgical evidence which I can’t go into detail into (I am hoping the owner will post it here openly but thus far has has not) where the cam interface was found to be well trashed (usual instant verdict: “crap Lyco steel”) but lab tests found the material to be absolutely perfect. Verdict: unknown, but given the unknown history before the current ownership, corrosion via long periods of inactivity seems to be the only possibility. Well, that or somebody putting grinding paste into the oil…
And let’s be brutally frank about this. How often can you 100% vouch for the previous owner’s usage pattern? Logbooks mean only what he wrote into them… So much in GA is just air and more air…
Or the history before the school bought it.
Cessna factory, then ferry flight.
Always hangared, around 300h p.a. per aircraft. Not a lot of activity during Jan/Feb though, due to weather. No camguard.
But the thing is the rotax 912 at a microlight school not to far from us. Which I assume was equally abused did 3600 hours before being sold to a private owner. And in my experience of 912 that’s not unusual.
Cessna factory, then ferry flight.
I had Bathman’s one in mind.
But the thing is the rotax 912 at a microlight school not to far from us
That’s a different engine. Doesn’t the Rotax have the crankcase vented into the inlet manifold, like cars have? Also a Rotax doesn’t have that cam interface weak spot which is the classic “trash a Lycoming” starting point.
Which I assume was equally abused did 3600 hours
Sadly I don’t think one can assume that. There are very particular patterns to certain kinds of renters in certain situations. To say more would open me to accusations of over-generalising 
but I have seen all kinds of crazy stuff of flying once a week for the last 15 years. I know of one school with a (nice) Rotax aircraft and sure as hell they would not be renting that one to the same people who they would rent a C152 to.
I am doing the Annual tomorrow on the TB20… 50% Shell W80, 50% Shell 15W50, Camguard
The cost of the oil barely features in operating costs, on any plane, IMHO.
It’s ridiculous to think that Total oil could be responsible for engine damage. It has the same specification and you could just as well believe in homeopathy if you say that.
I use D100 + Camguard and i am pretty sure there’s not much more that can be done oil-wise
