What is normal oil consumption?

I have a 2005 Robinson R-44 Clipper II that I purchased new. The engine is a 540 injected Lycoming. I broke the engine in on mineral oil as suggested and changed to ashless oil after the initial 50 hours of break in. The ship has used about 1 quart of oil per every four hours flown on average from day one and continues today (there are currently 240 hours on the ship). During the 200-hour inspection, we checked compression and found all cylinders to have excellent compression. I have always noticed oil coming out of the breather after shutdown and have also noticed oil on the rear cross tube, which would indicate the loss of oil during flight. I have never seen blue or any unusual smoke out of the exhaust. The plugs looked perfect on the 100-hour and 200-hour inspection with no dark spots or indication of burned oil. The ship has plenty of power and always starts and runs great.

What is normal oil usage? Is this excessive oil consumption? The ship is under warranty until August 2007. What do you think? Is this a problem that I should address or is this OK?


Bristol, Conn.

After reading your question regarding the oil consumption on your Robinson R-44 Clipper II, I can tell you that you have no problem if the information you provided is as you stated.

The question of oil consumption is a question that crosses all models of Lycoming engines and is probably the most difficult to really nail down. To answer your specific question, “”What is normal oil usage?”” all I can say is I don’t think there is such a thing. There are so many contributing factors that I don’t think anyone can give any specific consumption amount, but reasonable consumption is anything from 1 quart in three to four hours to better than a quart in 10 to 12 hours or more.

On the specific model IO-540-AE1A5 in your Robinson, if you take a look in the Lycoming Operators Manual Part Number 60297-10, you’ll see that the maximum oil consumption at rated power is .78 quarts per hour. At 75% power it is .58 quarts per hour and .51 quarts per hour at 65% power. I realize these figures are more closely associated with fixed wing aircraft, but still apply to your engine. From this information we can answer your question that you do not have excessive oil consumption. If we look at the consumption numbers you mentioned, I’d say you are well within the specification for your engine model. Even though I can understand why you may be somewhat upset because of the oil on the rear cross tube and a slight drip from the breather, I’d say this is something you may have to live with, which probably isn’t what you wanted to hear.

From all of the additional information you provided I’d say your engine is performing normally and is confirmed by your comment on the spark plugs. If there were a problem with consumption we’d probably see some telltale signs on the plugs, especially the lower plugs after some ground running at lower rpms or when doing a mag check.

I’d suggest that you continue to operate the aircraft as you have been and continue to record the oil usage. Other than that, I’d just keep on keeping on.

Paul, first, thanks for your help. My Lycoming O-360 A-1D in a Mooney M-20C currently has a Stratoflex Teflon flex line with stainless braided cover installed for the prop gov oil return line. The Lycoming overhaul manual lists two part numbers for this line. I assume one of them is the stainless solid line. Is the other this flex line? Can you refer me to the SI or SB that refers to this line? Thanks.


via email

Brent, thanks for your recent question. I’m hopeful this answer will not only help you, but others as well.

For many years Lycoming only furnished a solid stainless steel line for those engines that utilize a rear mounted governor like your O-360-A1D. I suspect the oil line part numbers listed in the Lycoming Overhaul Manual you mentioned are those of the stainless steel lines that were used for many years and not for the flex line currently on your engine. As a matter of fact, depending on the age of the line, it may still be of the old configuration that used aluminum connecting nuts. I’d recommend you review a copy of Lycoming Service Instruction 1435 dated April 1986, which also will provide you with the correct information on the flex line you mentioned.

SI 1435 covers two subjects, but the information you are seeking is covered in the latter part of the SI. The flex line information is addressed in SI 1435, Supplement No. 1 dated April 1990.

Just as a precaution, I’d like you to verify that what you have is the latest configuration addressed in the Service Instruction, which calls for using both steel elbow on the front of the crankcase and on the attaching nuts of the oil line being used to connect this line to the governor on the rear of the engine.

This should give you enough information to satisfy your question or at least direct you to where the information may be found.

Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.

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