I'm done with the 2,700 RPM climb to cruise

[Bartman]

I have been following oil consumption in my IO-360 powered J lately. For years I have been climbing at 2700 RPM to my usual cruise altitude of anywhere from 6K to 12K with the majority of longer trips around 10K. One of the air-oil separators was installed long before I purchased in 2007 but don't remember which one. In an effort to decrease consumption I lowered my minimum to 5 quarts instead of 6. That made a small difference, but I also noted that it does not lose oil on long trips at the same hourly rate. I lose the same amount of oil on a 1 hour flight as a 4 hour flight with all cruise at 2,450 to 2,500 RPM regardless of altitude.

Several few weeks ago I made a decision to reduce power at 1,000 feet AGL and then climb at 2,600 RPM which made a little difference with some decrease in consumption. Then I decided to climb at 2,500 and it hade a huge difference. I was adding about 1/2 to 1 quart every other flight to keep it at 6 quarts and most of those are 50 minute flights to work. Lowering the limit to 5 qts didn't really make a whole lot of difference. Now over the past 10 hours climbing at 2,500 and only adding at 5 quarts on the dipstick and on longer trips I have only added 1 quart. 

I read the Deskins Pelican Perch articles many years ago which is why I had been climbing at max RPM, and have gone back and read some of them again from time to time. I'm sure full power balls to the wall makes sense on some aircraft, but mine likes 2,500 RPM climb better with regard to oil consumption with absolutely no issues with oil temp or CHT.  The climb rate suffers slightly at higher altitude but not much and I was still 250-300 fpm thru 10K at max gross takeoff at 90 degrees.  To get up to 15K last week I did have to go to 2,600 for the last couple thousand feet. 

[Skates97]

Interesting observation. When I first got my plane I was backing off to 2,500 after takeoff and I would see about 1 qt every 8-10 hours. (Recommended climb setting in my original POH is 2,500 and in the 1977 M20C POH is 2,600). I keep it at 6qts and would add 1/2-1 qt to bring it back to 6qts when doing pre-flight if I was down to 5-5 1/2 qts. After reading the same article that you mentioned as well as a number of posts here I had been climbing at 2,700 for the first 3-4,000' or so and then backing off to 2,600 for the remainder of the climb. (Yes, I have read all of the posts about how it doesn't hurt the engine so I don't need a refresher course on that. )

I have noticed that I have been adding a quart every 4-5 hours since making that change. I don't think it is burning any more oil, there isn't any dark soot down the right side of the plane, just the white/powdery deposits that from what I have read on here is normal and good. I have noticed additional oily residue on the left side (assuming coming from the breather) and there has been a little more of a puddle under the breather on my hangar floor than when I was climbing at 2,500. My completely unscientific thought is that at the higher rpm perhaps it pushes more out of the breather and running at a higher rpm for a longer period of time the cumulative effect is that I go through more oil.

The more experienced/knowledgeable folks can offer their input, but I think I will go back to a 2,500 rpm climb for a few flights and see if it takes me back to the 1qt every 8-10 hours. 

[Hank]

I've been climbing WOT / 2700 to altitude, be it 3000 or 10,000 msl for ten years and over 600 tach hours in my C. I have never had a puddle in my hangar floor . . . except before I resealed the tanks. A puddle under the engine would worry me! Especially if it is oil . . .

One thing I've noticed is that my oil usage is lowest right after a change, and each succeeding quart comes a little quicker. The first quart is usually good for 10-12 hours, the last one probably 6-8 hours.

[XXX]

Bartman, funny you should post this tonight. Im sitting at I19 (Dayton area Ohio) waiting for my daughter to pick me up after a 4.7 hour flight from Ocala, FL. This flight, I reduced power for my climb to 2500 just after departure. Left with 6.5 qts, arrived with 6. Last flight climbed balls to the wall left with 6.5 and arrived with 4.75 Similar altitudes, similar times, same distance. This flight was an experiment for me too. Yes, I'm done with 2700 climb to cruise as well. 

[KLRDMD]

Do you think it is burning the oil, blowing it out, or what ?

I climb at 2700 RPM and 37" (231) to altitude and put in one quart between oil changes that I normally do around 35 hours. I just put a quart in today after 25 hours on the oil.

[Raptor05121]

I'm going to try this as well.

[Skates97]

1 hour ago, Hank said:

I've been climbing WOT / 2700 to altitude, be it 3000 or 10,000 msl for ten years and over 600 tach hours in my C. I have never had a puddle in my hangar floor . . . except before I resealed the tanks. A puddle under the engine would worry me! Especially if it is oil . . .

One thing I've noticed is that my oil usage is lowest right after a change, and each succeeding quart comes a little quicker. The first quart is usually good for 10-12 hours, the last one probably 6-8 hours.

Puddle is probably the wrong word. When I was climbing at 2,500 there would be a spot right below the breather hose where it sticks out of the left cowl flap opening where the dust would accumulate, sticking to the small spot where the oil would drip and spread from. Since climbing at a higher rpm the spot is a little bigger, maybe about 2" in diameter when the plane has sat for a couple of days after a flight, and you can see a little wetness on the floor. It isn't an oil leak, it is directly below the breather hose and it is obvious that is where it is coming from. 

35 minutes ago, Chupacabra said:

Bartman, funny you should post this tonight. Im sitting at I19 (Dayton area Ohio) waiting for my daughter to pick me up after a 4.7 hour flight from Ocala, FL. This flight, I reduced power for my climb to 2500 just after departure. Left with 6.5 qts, arrived with 6. Last flight climbed balls to the wall left with 6.5 and arrived with 4.75 Similar altitudes, similar times, same distance. This flight was an experiment for me too. Yes, I'm done with 2700 climb to cruise as well. 

I'm planning on the same type of experiment and will see what it yields for me.

26 minutes ago, KLRDMD said:

Do you think it is burning the oil, blowing it out, or what ?

I climb at 2700 RPM and 37" (231) to altitude and put in one quart between oil changes that I normally do around 35 hours. I just put a quart in today after 25 hours on the oil.

In my case, I think it is blowing out the breather judging from the extra residue down the left side of the plane and the extra that I notice below the breather hose after flights.

[jetdriven]

If your engine is really burning or blowing out aquart per hour at 2700 RPM I'd investigate that, because it isn't normal. 

Edited July 10, 2017 by jetdriven

[aaronk25]

The difference mechanically from 2700 to 2500 isn't much, hard time considering that is the reason for a delta in oil consumption/loss. I cruise at 2700 up high lots and don't see any difference in burn.


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[ArtVandelay]

The difference mechanically from 2700 to 2500 isn't much

I disagree, from the sound it makes, at 2700 it seems to be screaming, at 2500 it's humming. I even back it off on takeoff a turn to about 2650.
When the oil gets 30+ hours on it the consumption starts to increase, I end up with oil dripping off the nose gear onto the tire, and I have the 1 piece belly and get oil dripping from the rear seam. Muffler is clean. Also have some dripping from the breather hose.

[aaronk25]

The higher noise level at 2700 is mostly prop noise. Some experimental and heli engines turn even more rpms. Not sure what you having going on. Hope it all works out.


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[Bartman]

I do not have a puddle of oil under the belly, exhaust is clean, compressions have always been in the 70's in all cylinders, but I do have some oil drips under the breather hose and the belly and gear doors get oily.  I change oil at 35 hrs and fill with 7quarts and a new filter. Don't have to add anything until 6-8 hours, but increases after that. I also switched from the Aeroshell 15-50 that I had been using to W100 Plus so that may make a difference too. 

I am nearing 35 hrs on this oil change and have added 4.5 quarts total so far with this approach.  I calculate one quart every 7 hours and I'm pleased with that. 

[jetdriven]

One of our members, @testwest wrote a masters level thesis with tons of data that shows that a reduced power climb uses more time, fuel, and distance than a 2700 RPM, full throttle, Target EGT, Vz profile climb. IIRC it was an extra 20 knots block speed for the climb. For free. Real data.  You save the cost of a quart of oil per cycle in fuel. But I'd still check the engine out, using an extra half quart of oil for a half-hour climb is not normal.

[MyNameIsNobody]

I climb at max RPM and 120 indicated because I want the engine to be happy and I want to get to cooler air and cruise configuration more quickly.  Do what you want with power on climb, but I think the oil usage because of RPM in climb is likely not "the issue".  I don't lean in climb.  I like the lower cylinder temps from the fuel.  5-10LOP works out to 297-315 cylinder temps in cruise.  I don't see anything over 335 in climb.  Oil is cheap compared to an engine.  I feed to maintain six indicated.

[Brian Scranton]

When you guys say you climb at 120 IAS, at what altitude is that? I get ~400fpm at 100mph IAS...25/2700

 

[INA201]

Just a thought here. I saw a similar issue as well and will climb at either 2500 or 2700 depending on the day.  My conclusion without paying a lot of attention to oil usage is that the climb attitude makes more difference than the RPM. If you climb at the same airspeed then your attitude will be steeper at 2700. When I'm playing around and doing steep attitude climbs it seems like I use more oil. 

[Bob_Belville]

24 minutes ago, Brian Scranton said:

When you guys say you climb at 120 IAS, at what altitude is that? I get ~400fpm at 100mph IAS...25/2700

 

I average 500 fpm or a little more at ~115 ktas. But I have an E = lower weight to HP than your mid body. (At Vy I should see almost 1000 fpm through 5000' or higher unless it's very hot.)

[Brian Scranton]

Just now, Bob_Belville said:

I average 500 fpm or a little more at ~115 ktas. But I have an E = lower weight to HP than your mid body. (At Vy I should see almost 1000 fpm through 5000' or higher unless it's very hot.)

Thanks Bob! I depart my home field at 5750'...and my numbers are always lower than many I see here. I liken it to: altitude, DA, max gross flying, mid body, dirty bird (lots of antennas)...

[Mooneymite]

When the big recips were king, most catastrophic engine failure occurred at takeoff power.  Climb power was always reduced.  TBO was greatly reduced by high power settings.

While max rpm gives better performance numbers, I often wonder what the relibility/longevity numbers would reveal on engines climbing at POH rpm vs max rpm.

Anyone know?

[jetdriven]

These aren't turbo compound boosted engines making over 1HP per cubic inch.  They have time limits for a reason.  Naturally aspirated engines like we have do not have a Takeoff or a METO rating. They can run at 2700 RPM all day long, the helicopter versions run 3200 RPM.

2700 RPM is even listed as a cruise power setting in the POH. We shouldn't apply R-3350 procedures to a IO-360 anymore than we should apply limitations for boat engines or diesels. They are completely different animals. 

I do know that pulling the prop RPM back at full throttle raises the cylinder pressure and CHT. Pulling the throttle back to "26-26" or some arbitrary number robs you of 1/4 to 1/3rd of your climb capability. Airplanes climb because of excess power, and any reduction comes from there first.  So it takes longer, burns more fuel and takes more distance. More time spent in the ROP climb configure instead of lean cruise. You lose in every category except it "doesn't sound so much like its screaming" and the tach isn't close to the red. Let the data others have worked to produce, tell you how to do it. 

Edited July 10, 2017 by jetdriven

[nels]

4 hours ago, INA201 said:

Just a thought here. I saw a similar issue as well and will climb at either 2500 or 2700 depending on the day.  My conclusion without paying a lot of attention to oil usage is that the climb attitude makes more difference than the RPM. If you climb at the same airspeed then your attitude will be steeper at 2700. When I'm playing around and doing steep attitude climbs it seems like I use more oil. 

I think this may have something to do with it. Higher rpm during climb typically means a steeper climb which means oil at the back of the oil pan is deeper than at cruise or a lower rpm climb. Maybe the vent puts more oil over board at this time just as it typically does when you fill it to eight quarts. 

[steingar]

Maybe they knew something when they wrote this into my owners manual.

[jetdriven]

1 hour ago, nels said:

I think this may have something to do with it. Higher rpm during climb typically means a steeper climb which means oil at the back of the oil pan is deeper than at cruise or a lower rpm climb. Maybe the vent puts more oil over board at this time just as it typically does when you fill it to eight quarts. 

What's the mechanism for a higher climb attitude putting more oil overboard? I can't see that. 

[Bartman]

34 minutes ago, jetdriven said:

What's the mechanism for a higher climb attitude putting more oil overboard? I can't see that. 

Here are two questions we all want to know and may help answer your question and many others...

What is the mechanism flor throwing out anything over 6 quarts ?

Since almost everyone who has ever flown behind the Lycoming 360 knows this by experience, then why does Lycoming recommend we put in 8 quarts ?

[KLRDMD]

7 hours ago, Brian Scranton said:

When you guys say you climb at 120 IAS, at what altitude is that? I get ~400fpm at 100mph IAS...25/2700

I generally climb at 120KIAS from the runway up and get 800 fpm to whatever altitude I am cruising at. But that's a 231 at 2700 RPM and 37" MP.