Question for Paul McBride, General Aviation News‘ engines expert: I have a Lycoming IO-540 engine with what Blackstone Laboratories says are consistently somewhat high metal readings.
Someone I spoke with at Lycoming support awhile back told me the numbers are not really out of line.
Can you give me Lycoming’s limits on Aluminum (Al), Iron (Fe), Chromium (Cr) and Copper (Cu)? Cu may be high due to AeroShell Oil Plus.
I am going to plot the readings I have, but they all look stable, just a bit high.
Carl
Paul’s Answer: Carl, if you don’t mind, I’m going to use your question as an example of how difficult it is to provide a reasonable answer to a question like yours.
This is all on me, but I believe once you understand where I’m coming from, it’ll give you — and hopefully other readers — a better starting point when asking technical questions, regardless of the product.
The most important thing missing from your question is sufficient information so that I have some history of the engine involved. Providing information, such as specific engine model, specific engine serial number, and total time since new, remanufacture, or field overhaul, is very important. A short summary of the engine’s history, such as when the situation was discovered and whether or not it came following any recently completed maintenance, is also critical.
As an example, I’ve seen complaints of metal contamination in the past that were discovered shortly after an engine was replaced due to a previous engine failure, only to learn that the previous engine failed because of metal contamination, but the oil cooler and attaching oil lines were never replaced (flushing doesn’t always work).
Not smart, and the result was contamination of the replacement engine.
Another important thing to relate is if you’ve had oil samples tested, have the samples been taken at the same number of operating hours consistently?
Getting back to your basic question, I’d strongly recommend you plot the readings from several oil analysis reports you’ve gotten. The key to this type of situation is how the numbers come out after several samples have been tested.
If all the numbers remain relatively constant, this is what we’re looking for.
If from one sample to another Fe or Al has a sharp increase, then this is when we begin to become concerned.
If all of the samples have been taken consistently, and you see a sharp rise in some of the elements, I’d suggest you run the engine to the normal operating temperature and after shutting it down, drain the oil and take your sample at the mid-drain point. Check the engine oil filter and or the oil pressure screen and clean or replace the filter as required. Operate the engine for a period of about 10 hours and repeat.
If the engine is manufacturing metal, this simple check will give you enough information to make a decision as to whether the engine actually does have a serious problem.
Comparing samples over a period of time is the only way to really learn the condition of the engine.
To my knowledge, Lycoming does not have any hard and fast numbers relating to how much is too much, because every situation is different. Again, the secret to analyzing oil samples is consistent readings.
I apologize if I’ve been a bit rough on you Carl, but please understand that the more information you can provide up front regarding technical questions, the better the chance that you’ll get a good response.
For a piston aircraft, learn to examine your filter, monitor oil consumption, borescope your cylinders, and interpret engine monitor data. Don’t waste time and money on useless oil analysis – it adds nothing.
For a piston aircraft, learn to examine your filter, monitor oil consumption, borescope your cylinders, and interpret engine monitor data. Don’t waste time and money on useless oil analysis – it adds nothing.
As an”old guy” 55+yrs flying, mechanicing n running an old A&P school for a few years. I won’t let my small bore Continental friends run Avgas without ALCOR TCP. I’m not selling anything. I think Cam guard does what it says, Marvel doesn’t hurt but the TCP seems to do what it claims and simply put, keeps the lead in the exhaust/vapor long enough to get it out the pipe vs condensing on valves.
Unleaded autogas also solves the problem but I’ve burned Avgas that sat in the barrel on a S American crop dusters stash for 5+ years without degrading. Not sure 5 MONTHS under those conditions will hold for today’s autogas blends. I understand why. Just be careful what you wish for LOL 🙄
I recall a meeting back in the early 1990’s with Lycoming engineers and quality people, and the consent was to NEVER use synthetic oil when burning leaded Avgas, which was all there was back then. The additives in the synthetic oil would not hold lead or lead byproducts in suspension, leading to the “gray mud” syndrome not only in Lycoming engines, but any make and model of piston aero engine. I can’t recall now, but I think Lycoming issued a Service Bulletin or Service Letter on the issue.
This is why I always liked having oil screens instead of filters, especially the pleated screen type that the IO-470 used to have. It’s easy to inspect. Besides, if an engine decides to make metal, no oil filter is going to save it!
opps sorry I ment to say idling above 1000RPM will help burn all the fuel to prevent build up…..
Thanks ……did not have coffee yet!!!
Sorry I forgot to add while waiting for take off, always keep the engine RPM above 1000RPM so the cylinders do not get too cool. This will prevent all fuel to be burned efficiently and keep the lead salts from building up in the cylinder……………..
I have always used Marvel Mystery oil in the fuel and CamGuard in the oil. An oil that is not 50% synthetic is recommended as the lead in 100LL and synthetic oil produces a gray sludge over time.
Proper leaning and engine operation is also key to prevent stuck valves. Preheating with temperatures below 45 degrees is important.
Obviously when lead free fuel finally comes out, a lot of our problems will go away. The only unknown is will the new fuel degrade like auto fuel?
I have been told MM oil and CamGuard to little to prevent stuck valves…..??
I don’t know if that is true other then aircraft I personally own and fly have not had a stuck valve yet…..
Thanks
Does it work?
Paul,
I see in the Blackstone report that the lead levels are in the 6,000 – 7,000 ppm range.!
Do you see that causing any lead issues with the exhaust valve guides ?
The lead levels in our GO-300 jumped to 3,000 ppm from 1,500 ppm, when our oil use dropped from 3 hrs per qt to 9 hrs per qt., after a cylinder change.
After about 200 hours with the higher lead levels, the exhaust valve stuck open in #3 cylinder, which has 350 hrs on it. I had to ream the exhaust vale guide to allow the vale to again move easily .
I checked #1 and #5 and both were sticking and reamed those . These cylinders have 350 and 250 hrs on them.
My current plan is to reduce the oil change interval to 30 hours. If the lead is still high, I’ll go to 25 hrs.
BTW, the plugs are clean with no lead buildup, but the exhaust stacks have a lot of gray lead deposits.
Do you have any recommendations ?
I’d love to be using G100UL asap.!!