IO 520 oil burn

7 hours 25 minutes ago #3469 by Grant W
Replied by Grant W on topic IO 520 oil burn
Thanks for the quick reply, Steve. The IO-550-D has a 12 quart sump like my previous IO-520-D. I always maintained the oil level at 10 quarts on the 520-D and rarely had to add a quart between oil changes.

Consequently we've always serviced the oil to 10 quarts (indicated on the dipstick) after an oil change, and we've done the same on the 550-D.

At ~16 hours we did the first oil change to get a look at the filter and do a borescope of all the cylinders. All compressions were over 70, the plugs looked good and the cross hatching was apparent on all cylinder walls. Aside from some very minor oil seeps that we corrected, there was no obvious indication of oil going anywhere other than through the cylinders themselves. The belly was clean, no abnormal amount of soot in the exhaust stack, etc.

After allowing the airplane to sit for a few days, I'm measuring just a bit above 8 quarts indicated on the dipstick in 7.8 hours since the oil change. So about a quart every four hours.

I'm inclined to keep running it for a few more hours to see if it stabilizes at or around 8 quarts (which still seems low to me).

At that first oil change we continued with straight Aeroshell 100 mineral oil since we thought the consumption was still high. It hasn't gotten any worse, it just hasn't gotten any better. So has the consumption (rate) stabilized at this point? Maybe it has, and we just need to switch back to ashless dispersant and see if the type of oil has any bearing on the consumption rate.

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5 days 20 hours ago #3450 by STEVE ELLS
Replied by STEVE ELLS on topic IO 520 oil burn
Hi Grant;

It's unusual for a factory reman to be using oil at that rate.

Let me ask a question. Are you filling the oil sump to the full mark (I think it's 9 or 10 quarts in that engine)?

If you are, you should try working to maintain the oil level at a lower level, such as 7 quarts or 8 quarts.
These engines will always use oil since they, being air cooled are built with looser internal tolerances than and auto engine simply because they have to perform from temperatures ranging from +20 deg F up to +110 deg F OATs.

And since they are looser, they tend to "blow out" any oil above an engine's optimum level. Once that optimum level for your engine is found, your oil consumption should decrease considerably.

Broken in is defined as the point where the oil consumption stabilizes. Once it stabilizes you can switch to the ashless dispersant oil of you choice.

I hope this answers your question.
If you still have questions, get back to me.


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6 days 3 hours ago #3447 by Grant W
Replied by Grant W on topic IO 520 oil burn
Hi Steve, I am putting time on a factory rebuilt IO-550 and at around 20 hours on the motor I'm still adding about a quart every 4 or 5 hours. I noticed your remark regarding consumption continuing to decrease after a switch back to ashless dispersant oil.

Is the lower consumption a function of the oil type or the additional time on the motor during the break in period?

I'm still running mineral oil, and I guess you could say the consumption has stabilized at a quart every 5 hours. So should I switch back to AD oil at this point and see if the consumption rate continues to decrease?

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3 months 1 week ago #3327 by STEVE ELLS
Replied by STEVE ELLS on topic IO 520 oil burn
Hi Peter;
That is very high oil consumption.

Since the oil consumption jumped after a replacement cylinder was installed in the #1 position, I suggest I suggest you pull the bottom spark plug out of #1 cylinder to check for oil in the cylinder. It's possible that it is having oil control ring problems.

If your mechanic has a borescope, he/she may be able to detect high oil consumption by checking to see if there's oil pooled in the #1 cylinder.

Where did you get the cylinder that was recently installed on #1??
I suggest you call them and describe the huge change in oil consumption after installing a cylinder you got from them.

Let me know what they say.


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3 months 1 week ago #3326 by PETER MOLINARO
Replied by PETER MOLINARO on topic IO 520 oil burn
I have burned 9 quarts in the last 11 hours

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3 months 1 week ago #3325 by STEVE ELLS
Replied by STEVE ELLS on topic IO 520 oil burn
I'm extremely sorry that I haven't gotten back to you sooner.

When you say the other cylinders are now burning oil; what is the usage rate per hour?

Continental Motors has published a service letter with information on maximum oil usage.

Max oil consumption = .006 x % power

Where .006 is the brake specific oil consumption and maximum allowed oil consumption is based on pounds per brake horse power (lbs/BHP/Hr)

To calculate maximum oil consumption proceed as follows:

Using an IO-520-BB as example engine and maximum power is 285 BHP and 75% power is 214 BHP.

.006 x 75% = .006 x .75 = .0045 x 214 BHP = 9.63 LBS/hr

Oil weighs 7.5 lbs per gal at standard temperature and 1 quart of oil weighs 1.875

Therefore max allowable oil consumption would be 1 quart every 2 hours at 75% power.

You can use this formula to determine if your engine is using too much oil to be safe for flight.

I believe you'll find that your engine oil consumption will decrease after going back to non compounded (ashless dispersant) oil as you log more hours.

Please let me know what your oil consumption is now.

Again, I apologize for my lapse in communicating with you.,


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