O-470 oil consumption

[Mike Switzer]

The O-470 in our club's 182 is currently just below 1650 hours. Runs great, oil samples come back fine. On a recent long trip (just over 9 hours) it used about 3 quarts of oil, which is more than what it used to use. I doubt if it blew much out as we have not been filling it over 11 quarts because over 11 quarts it does blow it out.

Any thoughts? Given how it is running & the good oil sample results I was hoping to get it to 1800 hours or so before we had to do anything.

[Mike M]

One could consider looking up the type certificate data sheet for the engine to find the max oil consumption. .006 times percent power divided by 100 is the max pounds per horsepower per hour.

Or not.

[Mike Switzer]

Say What? I have the service manual for the engine & I don't see anything even remotely close to what you just posted. By that math is should use 0.01035 pounds of oil per hour, and I haven't ever seen a Continental of any size that used that little oil.

We have gone from using approx 1 qt every 5 hours or so (for the last several years) to 1 every 3 (unless something is being misreported). No leaks (for now, but they crop up every now & then. I think British Leyland engineers must have worked for Continental at some point)

[Jim Hann]

Any thoughts? Given how it is running & the good oil sample results I was hoping to get it to 1800 hours or so before we had to do anything.

Have you talked to Continental or Mike Busch?

[Mike Switzer]

Have you talked to Continental or Mike Busch?

No, I figured I would get plenty of input from the aircraft engine experts (including Mike) by posting here & on the AOPA forum, but this forum has been pretty quiet lately & the AOPA IT interns have managed to kill their whole website.

I have had the suggestion that I add marvel Mystery Oil (or similar) but I am already using Camguard (which is FAA approved) and I don't want to add something that might screw up the oil samples. This plane may sit for a couple weeks at a time (which is why I started using Camguard a couple years ago) when it flies most of the time it is for a fairly long trip.

[Mike M]

Say What? I have the service manual for the engine & I don't see anything even remotely close to what you just posted.

type certificate data sheet. that is not a service manual. you didn't say if your engine is an O470L or O470R, the one i found easiest was for the "R" model. attached, i hope, for your perusal. if not - trywww.tcmlink.com/EngSpecSheetDocs/O470R.pdf

[Mike Switzer]

I have the Type Certificate Data sheet for the engine. I think you must have a typo in your formula as it allows about 1/100th of the consumption of any other reference I have.

[Mike Switzer]

O470-R What I show is at 75% power roughly 2Q per hour is allowable. Not that i would like to fly one burning that much. The older models allow approx 4qt per hour at 75%.

[Mike Switzer]

The main issue here is that some of the club members have noticed that it is using more oil, while some others evidently NEVER check the oil after the first preflight of the day, as I have found it put away with as little as 6 quarts in it.

[WLIU]

I have spent a number hundreds of hours behind O-470's. I will suggest that a lot depends on how the engine is being run. When they are run hot they tend to get carbon build up in the ring grooves resulting in sticky rings that do not seal so well causing more oil to blow out the breather. When they are run cold, like around the pattern or just cruising around the neighborhood at low power these engines tend to get lead build up on the valve guides.

So I suggest that to answer your question you might do a compression check. That might show you that you are getting leakage past the rings.

Now some interesting questions about your O-470 and how it is flown are 1) do you have a JPI or other engine analyzer that reports temps on every cylinder, and 2) do you lean much? If the answer to question 1 is no and the answer to question 2 is yes, then I think that sticky rings is more and more likely given the time on the engine.

All of that said, you are loosing 1 qt every 3 hrs. Not a huge problem, but it is good that you are paying attention. You can certainly live with that until the next annual when you will get compression info.

I will note that some owners attempt to deal with this by installing an air-oil separator because they see oil on the belly and want to treat that symptom, i.e. make the ugly belly go away. Better to understand what your engine is telling you.

Best of luck,

Wes