What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

IO-375 Oil Consumption

Champ

Well Known Member
I now have 160 hrs on my IO-375-M1S and my oil consumption has consistently been 5 to 6 hr per quart since first flight. The engine is by AeroSport with ECI nickel carbide cylinders, Superior cold air sump and dual PMags, NGK BR8ES plugs. Performance has been flawless and I am very happy with it except for the oil consumption.

Background:
1. AeroSport had two test runs of 47 and 40 minutes with two 30 minute runs at 2700 rpm and 26?. Max CHT recorded was 339F. Aeroshell 100 mineral was used. Leak downs were #1-78, #2-78, #3-77, #4-78.
2. AeroSport ran the engine for an additional 2 hrs again cycling up to 30m runs at 2700 rpm and 26?. Max CHT recorded was 340F.
3. Approximately 6 ground runs prior to first flight with cowl off and CHTs never above 350F.
4. Diamond Aircraft?s test pilot flew the initial 5 hrs using Diamond?s break in procedure. The first 2.5 hrs were flown at 4000 to 5000ft, mostly at 2400 to 2700 rpm and 24.5 to 24.8?mp. Oil temps ran 185-195F with average CHT 358F.
5. Leak downs on last Condition Inspection at 120hr were #1-75, #2-76, #3-76, #4-78.
6. Aeroshell 100 Mineral was used for the first 50 hrs and Aeroshell 100W+ and 80W+ since as recommended by AeroSport.
7. It was 3.5 yr from when the engine was delivered til first flight (slooooow build). It was not technically pickled during this time but kept in a dry heated shop with desiccant plugs maintained, exhaust ports capped, minimally rotated and only near the end for spinner installation.
8. Normal cruise is LOP with oil temps around 180F.
9. Aircraft is normally flown once a week and is in a heated hanger.
10. No contaminants have been found in the oil screen at CI?s or filter at oil changes.
11. Oil samples were taken and stored at each oil change but have not been submitted for analysis.
12. Engine is run between 4.5 and 6.5 quarts.
13. No leaks or appreciable oil on the belly.
14. Oil does darken.
15. Can?t say the plugs or exhaust pipes show any real oil wetness or carbon build up.
16. Borescopes showed some scoring on the cylinder walls which AeroSport thought could come from power application before the cylinders were warm enough. Take off power is applied with oil temp above 100F. Borescopes show oil on cylinder walls after pistons are raised & lowered. Cyl 1 borescopes at 120 hr attached if interested

Bore1d.jpg
[/url][/IMG]

Bore1a.jpg
[/url][/IMG]

Questions:
1. Have others had similar experience with similar engines ? ie stroked, ECI, nickel carbide?
2. Could the test runs or first flights have glazed cylinders?
3. I seem to recall a VAF post where someone changed from Aeroshell single grade to Phillips multigrade and saw significantly lower oil consumption. Could this help?
4. Could the extended storage have been a problem?
5. Could my ground runs have been a problem?
6. I don?t plan on honing and reringing until oil consumption gets much worse as right now the cost of oil is less painful then the repair and the down time.
7. Would a crank case pressure test be worthwhile?
8. Is oil on the cylinder walls typical? Since compression rings are not wiping the cylinder walls unless the engine is firing.
9. Additional thoughts/advise/things to look for at my next annual?
 
This could just as easily be my post

I have the same exact engine except I have one Lightspeed and one Mag for ignition. I run Phillips 20W50 XC rather than the Aeroshell. Almost identical oil experience as yours. I have sent an oil sample off for analysis on every oil change since new and with the exception of some slightly elevated aluminum levels several hundred hours ago, they all come back with stellar results. No evidence of any scoring during the annual bore scope inspection. I have 537 hours on mine now and the oil consumption has increased closer to 4 hrs/qt.
I am planning to do a hone and re-ring at annual this year (and install 8.3 pistons).
 
I now have 160 hrs on my IO-375-M1S and my oil consumption has consistently been 5 to 6 hr per quart since first flight......
Sorry if I'm missing something, I did reread your post twice, but you are concerned with 5-6 hrs/qt?? And consistently since new? There were times when I'd have been thrilled with that. Compressions seem a little low, but certainly not alarming, for a 160 hr engine. Do you have a crankcase vent separator? If not, try the ASA. It performs very well and will likely help reduce the oil losses.

I've seen oil on the cyl walls like that. Doesn't concern me with the consistent compressions and overall low consumption.

Thinking about honing when you get closer to 2 hr/qt. Unless you just like the idea of doing major invasive surgery on your engine that carries a possibility of introducing worse problems.

2 cents worth of free Internet advice.
 
Last edited:
Is all of that dripping oil at the top of the cylinder? If the top, that is a lot of oil for a normal engine? Does the bottom plug have wet oil on it as well? Cyl walls look good. I would be looking for a source in the rocker box. Possibly a plugged return line or too much valve guide clearance. The scuffing is usually more like burnishing and should not be the source of oil consumption if you can still see the cross hatch running through them. If it is not scuffing, but scratching and the vertical lines are as deep or deeper than the cross hatch, they could be the source of oil above the rings. hard to tell from your pics, but it looks like typical scuffing to me.

Larry
 
Last edited:
Further to my original post

- Cylinders are 8.5:1
- The oil shown on Cyl 1 in the picture is the clearest shot showing this, but it is more or less typical of all cylinders. Its the oil that has been pushed up the wall when rotating the prop by hand. Probably after more than one rotation, if that makes any difference.
- I'm reluctant to put on a crankcase vent separator due to issues I've noted on VAF with these. It seems like a band aid solution to the real problem. And, so far the cost of oil is not breaking the bank or making cleaning the belly a big deal.
- Scuffs are the clearest picture of these and probably the worst of all cylinders.
- Plugged return line - possible, but on all four?
- Valve guide clearance - could be. Can I check this without pulling cylinders? Is this the wobble test? How do you do it?
 
I have brand new cylinders that look just like that on a O-200-A with the oil and some slight scoring too. I?m not worried because we replaced the jugs once before over borescope pictures and it turned out the scoring was very minor. Couldn?t even feel it, more of a cosmetic line. It looks worse on a borescope than real life. I would see if you are making Ferrous metal, if not carry on. I regretted pulling jugs over what we saw on a borescope. My new jugs have some oil in the jugs too. Compressions are 78/80 on all.
 
- Cylinders are 8.5:1
- The oil shown on Cyl 1 in the picture is the clearest shot showing this, but it is more or less typical of all cylinders. Its the oil that has been pushed up the wall when rotating the prop by hand. Probably after more than one rotation, if that makes any difference.
- I'm reluctant to put on a crankcase vent separator due to issues I've noted on VAF with these. It seems like a band aid solution to the real problem. And, so far the cost of oil is not breaking the bank or making cleaning the belly a big deal.
- Scuffs are the clearest picture of these and probably the worst of all cylinders.
- Plugged return line - possible, but on all four?
- Valve guide clearance - could be. Can I check this without pulling cylinders? Is this the wobble test? How do you do it?

Yes, wobble test will give indication of both too tight from carbon build up and too loose from worn or improperly machined guides. It is also possible you got a bad set of rings that just didn't break in properly. Also possible that the wrong type of ring was installed (several different metal and coating types for different cyl types - human error in build). In that cast a hone job on each cylinder and a new set of rings could resolve it. That much oil pooling in the cylinder can only be from a poor ring/wall interface or coming in from the valve / guide clearance, due to either a loose clearance or oil collecting in the rocker box.

Given this has been since overhaul, you really need to consider manufacturing defects and human error. Even the very best shops make occassional mistakes.

You could leave it and deal with the oil burn. Its not the highest consumption in the fleet.

Seems clear from the pics that you have a ring / wall or valve issue and the oil is getting burned in the chanber and not blown out the breather. A separator won't change much in the consumption rate.

Larry
 
Last edited:
For what it?s worth, my experience with the ECI cerminil cylinders is the same as yours. Same time on my io-360 with 8.5:1 cylinders with the same oil consumption. I also have some of the same scuffing. I pulled one cylinder that appeared to be the worst offender with the scuffing and realized the horoscope magnification makes it seem MUCH worse than it is. I?m still looking for the answer on reducing oil consumption. In my case I think I glazed the cylinders but not certain.
 
ECI Oil consumption

I thought I posted the first post, It's exactly the same problem I've been dealing with for quite sometime. I have a Titan 370 9.3 compression engine with 240 hours on it that has been burning 1 qt per 5 hours as long as I've had it, through the initial breaking in until I decided to hone and re-ring. I talked with four mech's, two said you can hone nickel carbide cylinders, two said you could not. Talked with the new Titan, Continental, they said you could and sent me a memo to pass on the mech on how to do it. Had it done, Turned out cylinders 1 and 2 were glazed. Initial breakin in went well, temps were down and seemed to run smoother. However, I was burning 1 quart per 2 hours initially and after 35 hours, now I'm burning 1 quart per 5 hours, exactly what I had before. When I took my cowl off the second oil change, I had oil on the bottom of the cowl, 1/2 ounce? and a wet number 4 EGT exhaust, never had that before, leaking valve guide? Now I'm talking with a different mech on possibly replacing the cylinders. The new mech I talked with was promoting nickel carbide cylinders but did say they are difficult to break in and suggested I would be happier with steel cylinders. My initial break in oil was Phillips 5/ 40 recommended by Titan. My second breakin in oil was pure mineral oil, just switched to Aeroshell 100 at 35 hours. Just FYI, Titan was purchased by Contiental, and they have repeatedly told me that they purchased Titan not the warranty. They have been extremely difficult to work with and the take away from me is there are much better choices of engines out there.
 
Curious

Chris,

Just curious when you say there are better choices of engines...are you meaning engines or engine suppliers?

And yes, I am fully aware that it is only your opinion...just curious is all.

Thanks
 
Another Observation

Everyone - Thanks for replies and interest in this thread.

The sniffle valve on my intake manifold seems to be leaving more than the usual stain on the hanger floor. The “stain” now contains about half a thimble full of oil. I did change from 100W+ to 80W+ prior to this becoming more noticeable. Coincidence?

I expect this is due to intake valve guide clearance and may be one of the reasons for my higher oil consumption.

I wonder if valve guide clearance has been a problem since day one, or, what could I have done to cause this on such a low time engine (160hr).

I’ll be doing a borescope soon and pay particular attention to valve stems and also contact AeroSport for their input.

Comments?
 
Last edited:
10 hours +

I have the same engine from Aerosport with Whirlwind prop.

During engine break in, for the first 2.5 hours or so I stayed at 2500-3500 feet and kept the engine between2700 and 2400 RPM. Manifold pressure was always an inch or 2 higher than RPM. (mostly WOT)

I was told by Doug at aerosport to overboost the engine the first 10 hours or so and then could back off. I've been at 10-12 hours per quart since then.
Also, I've never put more than 6 quarts in and seems to be happy around the 5 to 5.5 mark.

Maybe this will help in the future.
 
Last edited:
My Titan IO370 burned some oil the first few hrs. It is now at 52 hrs and is burning about a quart of Aeroshell W100 in 18 hrs. Used Phillips mineral oil for break-in and ran it hard with only two short ground runs before flight. I never put more than 6qts in because it will blow it out and I add oil when it gets down to 5.5 qts. Engine and WW prop are very smooth.
 
Last edited:
ROI of a hone and rering

I’m not sure the expense of a tear down, hone and rering is cost effective at that consumption level if no other issues are caused by it, or if it’s not pointing to other issues. That level of oil consumption may constitute and extra $1/flight hour of operating costs, which is a fraction of what fuel costs run. Factor in hanger rent and insurance costs, and I bet that level of oil consumption gets lost in the rounding error of the owning/flying equation. I’m not saying other less invasive diagnostics aren’t a good idea, and they may help decide if there are other factors in play, but just on its own merits, it’s within spec. In full disclosure, the issue you describe would drive me nuts too, and I’d be asking the same questions you are. ;)
 
Your post really hit home. I have a IO375 on an RV-7 with 160 hrs on it that has the exact same issues that you are having. I had Aero Sport Power hone and rering it 30hrs ago and it is still acting the same. Temps are great, runs great, starts great, but uses 1qt per 5hrs. Just wondering if you have found any answers to the problem or if you are still just living with it.
Thanks,
Trace B
 
Lycoming

I have the same exact engine except I have one Lightspeed and one Mag for ignition. I run Phillips 20W50 XC rather than the Aeroshell. Almost identical oil experience as yours. I have sent an oil sample off for analysis on every oil change since new and with the exception of some slightly elevated aluminum levels several hundred hours ago, they all come back with stellar results. No evidence of any scoring during the annual bore scope inspection. I have 537 hours on mine now and the oil consumption has increased closer to 4 hrs/qt.
I am planning to do a hone and re-ring at annual this year (and install 8.3 pistons).

So - an update: Instead of hone and re-ring last annual, I replaced all 4 cylinders with new Lycoming cylinders. 180 hours on the new cylinders now - using about 1 qt every 18 hours. Couldn't be happier. :)

edit: Oh I did install the 8.3 pistons as well.
 
Last edited:
Just as a data point, Titan 370/9.6CR from continental direct, about 150 hrs and still at about a quart/6hrs or so. Engine runs like a scalded dog and not worth the effort for me to try to improve it. Very happy with the engine despite the higher than "average" consumption.
 
Another data point...... ECI cylinders, Phillips 20-50 XC break-in and run, 6 quarts at oil change, 1 quart in 50 hours...... Correction!! One quart in 25 hours. change the oil at 50 hours with 4 quarts remaining.
 
Last edited:
Another data point...... ECI cylinders, Phillips 20-50 XC break-in and run, 6 quarts at oil change, 1 quart in 50 hours.

Impressive, can you give some more details? CR, Displacement, cylinder type, plain steel, cerminil?
 
Update

At 228 hr Tach (288 hr Hobbs) my oil consumption has not changed. Longer flights with not as many T&Gs seems to help. When I base consumption on Hobbs time instead of Tach (which is EFIS adjusted based on RPM), consumption goes from 6 to 7 hr/qt.

The engine starts, runs and performs great so I don't plan on taking any action yet.

I currently operate with Hartzell's RPM/MP restriction (because of my non CW crank/prop combination) but will be switching to a 3 blade MT. I was thinking of then pushing it over squared for a couple of hours to see if that might improve oil consumption.

CI is due the end of June so I'll take another look inside.
 
Last edited:
At 228 hr my oil consumption has not changed. Longer flights with not as many T&Gs seems to help. When I base consumption on Hobbs time instead of Tach (which is EFIS adjusted based on RPM), consumption goes from 6 to 7 hr/qt.

The engine starts, runs and performs great so I don't plan on taking any action yet.

I currently operate with Hartzell's RPM/MP restriction (because of my non CW crank/prop combination) but will be switching to a 3 blade MT. I was thinking of then pushing it over squared for a couple of hours to see if that might improve oil consumption.

CI is due the end of June so I'll take another look inside.

Do your research with the MT prop.. my experience was that the MT prop seemed slower in cruise than I was expecting.. I delivered a 200hp -7 with it, and only saw 150 knots TAS or so.. WOT, 11500 feet.. even at 8500 wasn't much faster, maybe 152 knots..I have heard from others that slower cruise speeds are the norm for MT. I did find it interesting that there was no noticeable speed difference in cruise from WOT and 2600rpm down to 2200rpm. The lower rpm allowed for more aggressive leaning, and more efficient cruise with no loss in speed.
 
Quote from MT - "+/- 2KTS for Cruise, better Climb and take off, smooth, lower noise". I'm expecting a cruise penalty. How much? Time will tell.
 
I have run my IO375 at 1" over square for 25 hrs and it did not help. That was done at the advice of Rob at Aero Sport Power. I have a hangar mate that has a RV-7A with the same engine that was completed 2 years before mine and he is burning 1qt in 16+ hrs.
 
Impressive, can you give some more details? CR, Displacement, cylinder type, plain steel, cerminil?

That was very impressive....:D I revised my post.

Break-in was per ECI instructions. Got the same burn rate on my PA28-151 with ECI cyl's. I pushed them hard right from the start, respecting temps.
 
Quote from MT - "+/- 2KTS for Cruise, better Climb and take off, smooth, lower noise". I'm expecting a cruise penalty. How much? Time will tell.

I don’t have any direct comparisons.. but I’ve heard others disappointed with the cruise speed.. I’d be interested to hear other (better) opinions and comparisons!
 
Back
Top