O-360 vs IO-360 durability/reliability

[Ashe]

I'm currently shopping some of the older M20's, and one of the things I am wary of is ownership costs.  While the market prices of the planes is well within my range right now, a high four-figure or five-figure maintenance bill is not.

It seems the most likely cause of something like that is the engine.  Right off the bat, I've noted that the O-360 runs about $5k to $8k less at overhaul, and is about $10k - $12k less to buy new than the 200hp IO-360.  While that is alot of money to me, it's not enough for me to dismiss the advantages of the injected motor.  If anything, it has me wishing the 180hp parallel valve IO-360 was an option.  Hopefully, this is something that only needs to be done once every 10 years of so, and averaged out that isn't too bad provided the motor can "go the distance".

In speaking with several well known MSC mechanics around the country as well as some engine shops, I've gotten mixed opinions on the two engines' durability.  About half the shops feel the 180hp engine is more durable than the 200hp one, attributing that to the lower compression putting less strain one the components.  Not that they feel the IO-360 is unreliable, but that it has a higher chance of needing a rebuild in the last 100 or 200 hours before TBO, and that it is unlikely to sail past TBO the way so many 180hp O/IO-360's will do.

However, the other half of the shops out there feel they're equally reliable and equally durable, and that the 200hp motor costs no more to own or maintain than the 180hp one except for costing more to rebuild.  Their opinion is that the difference in compression ratio (.2 I believe) is negligable and that it's more than made up for in improved cylinder head and fin design.

I'd really appreciate hearing owner experiences on the matter, as the most important thing to me is getting a plane I can afford to log some decent time in.

Ashe

[Parker_Woodruff]

I'd prefer the engine that can run lean of peak best...that's the IO-360.

[Ned Gravel]

Ashe:

I am with Parker on this one.  If you treat the engine well, keeping internal combustion pressures and cylinder head temperatures within reason, and IO 360 will go as long as an O 360.  You need an engine monitor to do that, and you have to be disciplined in your engine management technique.

My own engine went for overhaul at 1941 hours, just shy of the 2000 TBO, but that is because I did not appreciate these things until the last 150 hours or so of its life.  For the 150 hours previous to that, I was pushing the ICPs and temps with bad baffling and unknowingly agressive mixtures.  Before that (<1640 hours) it was someone else doing the same thing.

Hope this helps.

[Cruiser]

While a general historic view of these engines might provide some insight to their overall maintenance cost I believe there is too much variability in individual engines to have any meaningful impact on cost of ownership. More importantly would be the history your potential purchase has than any overall estimate might provide.

[Theo]

Quote: Cruiser

... I believe there is too much variability in individual engines to have any meaningful impact on cost of ownership.

[N601RX]

The big difference in the overhaul cost is the cylinders.  New IO360 angle valve cylinders are around $1900 each, while O360 cylinders are about 1/2 that.  The other 2 big ticket maintenance items are leaky fuel tanks and Prop.  These are around 10K each. I would look for newly sealed tanks, or bladders. A new prop would be a plus also with the recurrent AD on the old hubs.

[DaV8or]

I personally love not having to even think about carb heat and the hot starts aren't that bad.

[Barry]

I have a friend who has 25,000 hours, mostly in Mooneys. He told me that in that time he has had only 2 engine out problems, both in the IO-360. In both cases it was the fuel servo in the injection system. He also told me that you can run the 0-360 to 3000 hours, but you should only run the IO-360 10% over TBO.

I cannot vouch for my experience in this matter, but I deem it sage advise.

[rorythedog]

i flew my io-360 almost 2300 hrs and when it was overhauled it looked fine inside. i still feel better having had it done. the last 500 hours or so were lop. by the way, i added an air/oil separator at o/h and really like the benefits.

[Piloto]

While the O-360 may look like a lower cost option the IO-360 has a lower fuel cost. For the same air speed the IO-360 will be burning 2 gallons less at LOP than what is possible with the 0-360. At $5/gallon this would translate to about $10k saving over the engine life. The IO-360 also gives you greater range with the same amount of fuel.

José

[KSMooniac]

I agree that the advantages of the IO-360 running LOP by an educated pilot with good instrumentation will far outweigh the additional cost of the cylinders at overhaul time.  I also agree that whatever you choose, buying a good example that was operated well and regularly is the most important quality.  It is also possible to overhaul the IO-360 cylinders if needed for half the cost or less...one doesn't necessarily need to buy new ones.  Last year I had all 4 of mine IRAN'd for $2300 including new pistons (cost from the engine shop, no labor on the plane). 

Fuel tanks and props as mentioned above are potential "gotchas" too.

[DaV8or]

Quote: KSMooniac

 Last year I had all 4 of mine IRAN'd for $2300 including new pistons (cost from the engine shop, no labor on the plane).

[DaV8or]

Double post.

[DaV8or]

Sorry. Triple post. I kept getting the page of gibberish and wasn't sure if it really posted. This is the wackiest and buggiest forum I've ever been on. Oh well, adds character!

[KSMooniac]

Dave, I had low compression on two jugs thru the exhaust valves, and decided to get all 4 IRAN'd (Inspect & Repair As Necessary) to baseline them since they had 1400 hours on them before I got the plane.  I ended up with new seats and guides (properly ground), 1 new exhaust valve, 4 new pistons & rings, and a fresh honing.  This cured my compression issues as well as oil consumption and blow-by.  The pistons were discretionary and added $600 to the total.

[KSMooniac]

DP...same problem for me!

[N601RX]

Quote: KSMooniac

Dave, I had low compression on two jugs thru the exhaust valves, and decided to get all 4 IRAN'd (Inspect & Repair As Necessary) to baseline them since they had 1400 hours on them before I got the plane.  I ended up with new seats and guides (properly ground), 1 new exhaust valve, 4 new pistons & rings, and a fresh honing.  This cured my compression issues as well as oil consumption and blow-by.  The pistons were discretionary and added $600 to the total.

[KSMooniac]

A shop nearly local to me in Newton KS (Midwest Aircraft Services) did the cylinder work.  I R&R'd the cylinders and took them to the shop via pickup.

Oil consumption prior to the work @ ~1650 SMOH started at about 4 hrs/qt on fresh oil, and would deteriorate to 2 hrs/qt by 25 hours or so.  Afterwards, it is running about 15-18 hrs/qt and staying quite clean.  Some of the oil usage prior to the work was due to some leaking oil return lines that were replaced, though.