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  #1  
Old 07-10-2018, 10:51 AM
terrykohler terrykohler is offline
 
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Default Question for Engine Experts

Since new, my O320-D1A has burned less than a quart of oil every 25 hours.
Somewhere at just over 1,000 hours, I switched from Aeroshell 20W50 to Exxon Elite.
In the past 50 hours (now at about 1125), I've seen oil consumption rise to about one quart every 4-5 hours. One of the manuals shows .5 quarts per hour after break-in is the maximum.
Should I be concerned? What might be the cause of this sudden rise? Suggested actions?
Thanks,
Terry, CFI
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  #2  
Old 07-10-2018, 10:55 AM
maniago's Avatar
maniago maniago is offline
 
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Go back to Aeroshell.
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  #3  
Old 07-10-2018, 12:18 PM
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Mark Albery Mark Albery is offline
 
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Oil leaves the engine through either the breather, piston rings or valve guides if not through leaks which should be easier to spot.

So you shouldn't see a step change in oil consumption when you change brands or grades. It takes time for the effects of different oils to show up.

My first line of investigation would be a leak-down test, plug examination and borescope inspection. Maybe an oil analysis or check the paper filter element for metal.

Are you doing aerobatics? That would show as a trail from the breather.
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  #4  
Old 07-10-2018, 03:58 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Mark Albery View Post
Oil leaves the engine through either the breather, piston rings or valve guides if not through leaks which should be easier to spot.

So you shouldn't see a step change in oil consumption when you change brands or grades. It takes time for the effects of different oils to show up.

My first line of investigation would be a leak-down test, plug examination and borescope inspection. Maybe an oil analysis or check the paper filter element for metal.

Are you doing aerobatics? That would show as a trail from the breather.
+1

Seems improbable that a brand change can cause a significant increase in consumption, at least at the rate you are talking about. I also agree that a borescope, compression test are all in order to find the problem and I would add a valve wobble test (you're looking for excessive clearance, not the minimal clearance your looking for when testing for carbon build up) if you see the leaks in the intake or exhaust. With those rates and the rapid onset, my first guess would be a broken ring and commensurate blowby. I would start with a compression test. You can buy a tester for about $100. If that much oil is coming through a valve guide, usually exhaust, you'll see major build up of coked oil on the back side of the exhaust valve with a borescope inserted through the exhaust flange.

Have you noticed a marked increase in oil on the belly? That would point you to a blowby issue and exclude the valve issue. This would be verified by the compression test. Pull the plugs and look for wet plugs and oil pooling down by the cylinder top. Visible oil would point to a compromised ring / wall interface and a need for a hone/re-ring.

If it comes down to blowby with decent compression readings, you are ok to run it and watch the compressions more closely. 1 qt in 5 hours is not really uncommon with Lycomings. Not optimum, but not a death sentence.

Larry
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Last edited by lr172 : 07-10-2018 at 04:17 PM.
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  #5  
Old 07-11-2018, 04:30 AM
terrykohler terrykohler is offline
 
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Default Thanks Guys!

Rather than just accept the consumption rate, I'm probably going to start diagnostics this weekend following your suggestions. Fingers crossed that the fix is quick (another "20 minute" aviation job) and cheap (in aviationese, meaning less than 3 zeros on the price tag.)
Terry, CFI
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  #6  
Old 07-11-2018, 07:04 AM
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maniago maniago is offline
 
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What you did is typical of changing from a long term use of a mineral base stock to a synthetic stock. You cleaned out the inside of your engine, esp rings, of gum/oil shelac etc that was keeping it happy with the Aeroshell. And now your mid time engine is showing the wear that is typical of mineral oils, but at 2000hrs - cause thats when the gum cant keep the bore gaps filled. Used to happen all the time with auto engines, but less so these days since semi synth and full synth are the norm now - iow if you start with synth you stick with it always cause its way better lubrication and doesnt suffer from wear breakdown like mineral stock.

Bottom line with oils, is you dont change base stock type until you have a new engine to work with. Our air cooled lead engines are particularly susceptible to happy gumming. When we eventually get UL gas and can go to full synthetic, this issue will disappear...as it has in auto engines of all varieties.

From the info on Exxon Elite...."Exxon Aviation Oil Elite™ 20W-50 is a premium quality, semi-synthetic, ashless-dispersant aviation piston engine oil. It is formulated from select, highly refined mineral base oils, a polyalphaolefin synthetic base oil, and ashless performance additives providing outstanding engine cleanliness, wear protection, and corrosion protection. "

Note "outstanding engine cleanliness".

So now you got what you got. Fly it and monitor. No its not a bad engine, but your new oil burn will remain the same now. You can stay with the Exxon or go back to Aeroshell if you want as youve done the cleaning and it wont much matter wrt to oil burn......wrt to other wear, ie cam wear, lifters, exhaust valves, who knows.

Just my .02 tho.
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  #7  
Old 07-11-2018, 07:40 AM
tim2542 tim2542 is offline
 
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I agree it needs a borescope and leakdown test, time for a wobble test also. A real possibility you just have an engine problem, perhaps a broken ring or worn guide, probably nothing to do with the oil.
Tim Andres
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  #8  
Old 07-11-2018, 09:01 AM
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JonJay JonJay is offline
 
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If it helps, I switched from single grade to semi synthetic (aeroshell)in my 0-320-E2G at +\- 2000 hours. Oil usage was always minimal and remained that way after the switch.
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  #9  
Old 07-11-2018, 09:09 AM
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Mike S Mike S is offline
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Quote:
Originally Posted by maniago View Post
You cleaned out the inside of your engine, esp rings, of gum/oil shelac etc that was keeping it happy with the Aeroshell.
This is what a Shell rep told me would happen when I switched from straight mineral to detergent oil in my old Stinson-----20 some years ago.

He also said the consumption would go down as the parts wore in a bit with the gunk cleaned out.

He was right on both counts.

Perhaps you will see an improvement in oil consumption???
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  #10  
Old 07-11-2018, 11:13 AM
Charles in SC Charles in SC is online now
 
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There are folks on here with a lot more oil and engine smarts than me but here is what I would do. I would first look and see if one of the exhaust pipes looks like it is burning dirty. If so I would pulls a plug from each of the 2 cylinders on that header and see if they give you any info on where to look next. Another thing to look at is the crankcase vent. If it is venting into the exhaust stream the oil may be coming out there and being dissipated without you seeing it. If you cannot find anything wrong maybe one of your hangermate/friends may be messing with you. Those engines are pretty bullet proof. Good luck and let us know what you find.
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