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Oil consumption


Bravoman

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I am seeing oil consumption of about 1qt/5hrs. I run Aeroshell 15-50 with Camguard. My Bravo is a 98 with about 950 tt af & e. I know my plane, although very well kept and maintained, went through some periods of lower than optimal usage prior to my ownership. I am no mechanic, but assume that these engines burn a bit more oil on average than their normally aspirated cousins. I am curious as to what you all are experiencing In this regard and what you think is "normal".

Thanks, Frank

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1 quart per 5 hours isn't optimal but isn't terrible either. I get close to double that now in my NA 4 banger but was down to 1 qt per 1.5 hours a couple years ago before my overhaul. I would be more interested in the trends of your oil consumption. If it is all of a sudden burning more then usual you may have an issue. If it's been burning 1 qt per 5 for the last several years you are probably ok

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I fly a 98 Bravo as well with about 1000 hrs AF&E...engine also was subject to the crankshaft recall (which was basically a complete engine inspection with R&R of some other parts as well).  Oil consumption both before and after the crankshaft deal has been consistent at 1 qt for the first 10 hours, 1.5 quarts for the 2nd 10 hours, and then about 1 qt for the last 5 hours or so....that's 25 hours and then the cycle repeats with the oil/filter change.  I also find that operating at lower power settings - say 27/2400 - oil consumption goes up a little bit over the 30/2400 max cruise settings.

 

Btw, I use Aeroshell 15W-50 too...thinking of adding Camguard on next oil change.

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I fly a 98 Bravo as well with about 1000 hrs AF&E...engine also was subject to the crankshaft recall (which was basically a complete engine inspection with R&R of some other parts as well).  Oil consumption both before and after the crankshaft deal has been consistent at 1 qt for the first 10 hours, 1.5 quarts for the 2nd 10 hours, and then about 1 qt for the last 5 hours or so....that's 25 hours and then the cycle repeats with the oil/filter change.  I also find that operating at lower power settings - say 27/2400 - oil consumption goes up a little bit over the 30/2400 max cruise settings.

 

Btw, I use Aeroshell 15W-50 too...thinking of adding Camguard on next oil change.

 

I fly an 89 Bravo and have only been through one oil change and am about to do my 2nd. After my first oil change this is exactly what my oil consumption was - 20 hours from 10 to 8 quarts and it went up dramatically for the last 5 hours. It surprised me and I thought I hadn't recorded oil levels correctly. I'm changing the oil again this weekend (every 25 hours) and I now expect to see the same consumption rate.

My engine has ~1500 hours TTAF & E. The Bravo mod AF1B was done about 500 hours ago in 1998. There were about 8 years that it flew only 6-10 hours a year so when I had the prebuy done at Don Maxwell's in December of last year, he pulled a cylinder and looked at the cam and lifters for that cylinder. He found a little pitting but no corrosion and he said they looked excellent with no reason to think it wouldn't make TBO - or beyond. When the plane sat for so long it was in a dry climate in north Texas (Wichita Falls, TX).

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I've seen oil consumption as high as a litre (near a dammit a quart) in 4 hours, but more normally about 1 in 6 or 7.  High power high RPM seems to make it worse. FWIW, I'm about 1750 TTAFESN, but two cylinders have been replaced in that time, the other four are original.

 

It is quite difficult to get an accurate figure, as the oil level varies considerably depending on the attitude of the aircraft, and how long since it has last run. In my case, I try to minimise this by checking the oil before moving the aircraft from its regular spot in the hangar, normally before the first flight of the day (when it has probably not flown for a week or more). I also average the consumption over two measurements. Unfortunately I have seen a slight upward trend over the time I've had the aircraft, but this is now a fairly high time engine.

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I own a 98 as well.  I do not put over 8 quarts in it as it just seems to blow on the belly.  It won't burn any oil in the first 10 hours either and then 2 quarts over the next 15.  I normally run at 30/2400 1600TIT.  The engine has about 370 hours on a penyan overhaul.  

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I also have a Bravo with about 600 since new, I use 1 qt. between oil changes at 25-30 hrs. It is reasonably consistent. I fly cruise at 32/2400 tit 1625. My 1st 100 hours was at 34/2400 with similar use age. I've used a blend since new but just switched to camguard due to diminished flying hours.

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Wow, I see that oil consumption really varies, but I guess that is pretty typical for any make and model of plane. My compressions are all well into 70s and I have heard that consumption levels can improve if a plane that was not flown enough is used more regularly, so i am hoping to see a positive trend. These engines were designed for way more use than most of them get, and with a lot of birds flying only 30-50 hrs per yr it is amazing if it makes TBO.

On a side note gjkirsch mentioned that his engine was overhauled by Penn Yan. I think they turn out a first rate product. My toga was done by them back in 01 and has about 900 hrs on it smoh. It is a smooth running and really flawless engine. Everybody I know who has experience with them feels the same way. I have no doubt that my bravo engine will go to them when it comes time. My confidence level is much higher with a shop of this caliber vs a lycoming overhaul(although I understand that a factory reman is a much different product than an overhaul, but more expensive).

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I fly a 98 Bravo as well with about 1000 hrs AF&E...engine also was subject to the crankshaft recall (which was basically a complete engine inspection with R&R of some other parts as well).  Oil consumption both before and after the crankshaft deal has been consistent at 1 qt for the first 10 hours, 1.5 quarts for the 2nd 10 hours, and then about 1 qt for the last 5 hours or so....that's 25 hours and then the cycle repeats with the oil/filter change.  I also find that operating at lower power settings - say 27/2400 - oil consumption goes up a little bit over the 30/2400 max cruise settings.

 

Btw, I use Aeroshell 15W-50 too...thinking of adding Camguard on next oil change.

Interesting.  I am not a mechanic either, but I like to think I'm logical.  I do not understand why the rate of consumption should change the further you get from the oil change.  The only thing I can think of would be if the oil is getting thinner so it is easier to slide by the rings to get burned in the cylinder or to increase a leak rate somewhere else.  Other than that, given the same operating conditions you would think the rate of consumption should not change.

 

So what could do that?  Oil breaking down due to heat?  Something else getting in the oil and displacing the oil (fuel maybe)?  I don't know if an oil analysis looks for fuel in the oil or not.  I don't think ours does.

 

When do you check/add the oil?  Before the first flight of the day?  After the last flight?  Could it be you are adding oil before it has all drained down, put some in when you don't really need to, and then end up blowing some of it out the vent tube?

 

I don't know the answers, but it would be interesting to know if you figure it out.

 

On a related note, here is a link for an article on oil:

http://www.sportaviationonline.org/sportaviation/201101#pg98

 

And here is one for a webinar about oil (about an hour long):

 

http://www.eaavideo.org/video.aspx?v=1149666747001

 

Both are by Mike Busch and talk about the functions of oil, types of oil, etc.  The webinar goes into more depth and even makes suggested recommendations for oil use.  The discussion about types of oil starts about 23 minutes into the webinar.

 

Good luck figuring it out.

 

Bob

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I have also noticed that the rate of consumption increases as more hours go on the oil. This has been my experience with both aircraft I own. There isn't a huge increase, but it is something I have noticed. I am also at a loss as to the reason.

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  • 2 weeks later...

I also have a Bravo with about 600 since new, I use 1 qt. between oil changes at 25-30 hrs. It is reasonably consistent. I fly cruise at 32/2400 tit 1625. My 1st 100 hours was at 34/2400 with similar use age. I've used a blend since new but just switched to camguard due to diminished flying hours.

 

You're running too high a power setting in my opinion (85%).  TIT is OK. Your chances of making TBO at that setting... not good.

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I have also noticed that the rate of consumption increases as more hours go on the oil. This has been my experience with both aircraft I own. There isn't a huge increase, but it is something I have noticed. I am also at a loss as to the reason.

I have noticed this as well on the IO-360 and I think its due to the viscosity breaking down. Perhaps straight-weight oils do it worse than multigrades.

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To be more accurate and consistent you have to measure oil level at least one week after the last shutdown and at warm temperatures above 60F ambient. It takes at least one week for most of the oil to drain down from the engine upper section to the oil pan. On my IO-360 I see a difference in oil level of about 1/2 qt from the day after to about two weeks after the last shutdown. And this in Florida. A bigger engine in cold weather will take longer to drain. This explains some of the incosistencies you see in oil consumption.

 

José  

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Watched Mike Bush'a webinar and it's wonderful as always. My oil consumption for the last year went from a qt in 8 hours to a quart in 3.75-4 hours and his reliance on bore scopes really helps diagnose the problem. I know exactly where my issues is, it's the #4 intake valve guide, but for me benefit of saving a few bucks on oil is off set by the uneasy feeling a get about flying behind a engine that just had some major surgery.

As I write this I'm planing on leaving tomorrow AM from Merida, Mex crossing the gulf direct to Brownsville TX. Would I want to do it on a cylinder that just came apart......NO WAY! Besides as soon as the parts get replaced I start wearing out the new ones.....

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I've had my Bravo for about 12 years and the oil consumption has consistently been the same as I posted previously.  Why it consumes more oil as the time increases since the last oil change I cannot answer...but given that it has always been this way and the engine runs just fine (e.g., all compressions over 70), I'm not worried about the why!  I do know that the oil looks "trashed" at 25 hours...  I'd also point out that Lycoming did the crank replacement...and that came with new cylinder rings as part of the "discount" package for timely replacement.  No change in oil consumption pattern before or after the "quasi-overhaul."

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Don,

 

Do you mean bottom end of the engine or the top end? 

 

Andy

 

I'm not an engine expert.  Just an APS graduate.  85% power--not good.  Most likely the top of the engine due to high internal cylinder pressures at that high power setting.

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I've had my Bravo for about 12 years and the oil consumption has consistently been the same as I posted previously.  Why it consumes more oil as the time increases since the last oil change I cannot answer...but given that it has always been this way and the engine runs just fine (e.g., all compressions over 70), I'm not worried about the why!  I do know that the oil looks "trashed" at 25 hours...  I'd also point out that Lycoming did the crank replacement...and that came with new cylinder rings as part of the "discount" package for timely replacement.  No change in oil consumption pattern before or after the "quasi-overhaul."

Would it be possible that your oil could be getting diluted with fuel? Do you get oil analyses?

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I am at 1.5 quarts every 25 hours. (sometimes one, sometimes 2). Around the 25 hour mark, it always looks dirtier, which I assume is normal, then nice and clear after a change.

 

This is a probably a less accurate (but cheap!) test. As the hours go by, I check how the color changes, and if i can keep it mostly translucent (and not sludge black) up to around 20 hours, I would think that I am probably being good to my engine on its power settings for that oil change period.

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Maybe 15 years ago, I picked up a VHS put out by Shell that went into the longevity of their oil.  There was a direct and surprising correlation between oil temp and how long the oil would operate without breaking down.  If memory serves me correctly, at 185 it would last well past 50 hours and at 210 about 15 hours.

 

I certainly no expert (at anything it appears), but oil consumption in an air cooled aviation engine seems to vary greatly from engine to engine.  I had a friend who bought a new Skylane, non-turbo, and from day one, he burned a quart every 4 or 5 hours, all the way to TBO, which he made.  I do think that you will see some increase in consumption with both higher power settings and as you accumulate hours on the oil, both very natural, especially in a turbo aircraft.  I believe that the oil is exposed to the highest temps when it is going through the turbo, but I stand to be corrected on that.

 

As for Camguard, absolutely no empirical evidence that I have seen that it does any more for your engine than cat urine; but if it makes you feel better, go for it.

 

Jgreen

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Lycoming recommends the oil be changed at 25 hours for the engine in your Bravo. Not sure that running Camguard with Aeroshell 15w50 is really required, 15w50 has the equivalent Lycoming additive blended in to it already.

Clarence

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