To keep myself awake while watching TV in the evenings, I will read other aviation magazines or pull them up on the internet. One of the main purposes for this is to learn what the latest in aviation lubrication thinking is. The other is for a good laugh.
Recently, I was reading an article on aviation lubrication do’s and don’ts. The author had evidently worked in the aviation industry and had a few good points.
However, he made a statement to the effect that the only two ways to get rid of moisture in the oil was to change the oil or add this additive that, I assume, he was advertising or selling.
I read the article over several times, and he never mentioned the best way, which is evaporation. This is like talking about Dec. 25 and not mentioning Christmas (and I hope you all had a merry one).
The article went on and on about things that are nice to know and do, but missed the necessary things to do.
I have written about this many times, but people still do not understand the basics. If you want your engine to go full TBO, the two things you need to do to give you the best chance is make sure the oil temperature is around 180°F and fly your plane regularly.
If you do these two things, it does not really matter which oil or additive you use, how long you warm up your engine, how you hold your mouth when priming your engine, or any other of a long list of things to do.
When you get your oil temperature up to 180°F in level flight, as the oil goes through the engine it typically picks up about 50°F. This means that some of the oil in the engine, usually that coming off the underside of the pistons, is around 230°F. This is hot enough to boil off the water in the oil, since water boils at 212°F.
If you operate at these conditions for a while, all of the water in the oil is magically gone. You do not need to change the oil after every flight or add an expensive additive.
Now there is one other part of this method, and that is you will need to calibrate your oil temperature gauge.
Unfortunately, a lot of gauges only have a green band and others are way off calibration.
I strongly recommend that you take your oil temperature sending unit out and put it in a container of oil or water. Set the container on a hot plate and put a good thermometer in the liquid, along with your oil temp sensor. Now watch the thermometer and when your liquid gets to 180°F, look at what your gauge reads. If your gauge only has a green band, paint a mark at the 180°F point.
Now you will need to make changes to ensure that your engine runs near that 180°F mark in level flight. You may need to fix your baffles and seals or have your oil system bypass adjusted. You do not have to get exactly to 180°F, but you need to be near that range to boil off the moisture.
I do not have any problem with an approved additive or changing your oil more often. However, many people think that they do not have to bother with details like getting their oil temperature right if they use a miracle additive. My experience has shown this to be very poor and, in most cases, very expensive logic.
Thank you Ben. You are entirely correct in that the only way to avoid rust and corrosion inside an engine is to burn off the moisture by operating at full temp.
There is no magic juice on the market that can be a substitute.
As a side note, I see where operators will start their engines with their airplanes tied down, and run their engines for a few minutes (never reaching full op temp) and then shut down. When I ask them “why?” they state that they want to keep the engine lubricated since they do not fly often. That’s fine and dandy as far as lubricating the parts, but when I tell them they are creating more harm than good, they look at me as if I’m nuts
I then explain that if you only occasionally run an engine for a few minutes without bringing it to full operating temp, you are creating an even greater amount of moisture in the engine after shut down as the existing moisture has not been burned off and the luke warm runup has created even MORE moisture.
While flying the airplane is the best solution, the only other alternative is to run the engine for at least 20 minutes and taxi around the ramp during this time. My experience has shown that at least taxiing and doing a run up check (throughout the entire rpm range including static full power) until full temp is indicated will not only burn off moisture in the engine, but will also keep the spark plugs cleaner while confirming acceptable magneto performance.
Easy solution for finding 180^ on the “green arc” oil temp. gauge.
Thanks Ben….and Merry Christmas to all.
It would seem to me that the best way to keep the water out would be to not put any in. I, like many, have a fridge with a freezer in the back of the hangar. The relative humidity of the air in the freezer is less than 10%, the air in the fridge is about 10-15% RH. I use a little aquarium pump to draw the dry air from the freezer and pump it into the crankcase at the dipstick.
I placed a temp/RH sensor ($5 on eBay) in the overboard of the crankcase breather after a flight to see if this wa effective. It took about 30 minutes to drive the RH from 95% down to 10%.
The pump was about $30, and the hose about $10…eBay, of course. No dessicant to have to dry.
And should the FAA Hangar police question the aviationism of that big white thing in the back of the hangar, well, it is clearly being used as aviation support equipment.
Why complicate?
There’s a difference between water content in engine oil and water content in the air (relative humidity).
Your engine has oil which settles with gravity and so you have oil with air on top. The air, like all air, has moisture in suspension. What you have failed to realize is that by pumping freezing air into the crankcase you certainly are introducing air with less water in it, but you are also introducing cold air which will drop the temperature of the existing air inside the case, and encouraging moisture in that air to precipitate out.
The author is correct. Engine oil is hygroscopic and does absorb moisture, and his point is to fly the plane and by bringing oil up to normal temps you boil off that water and you coat moving parts with lubricating oil. This practice is of huge importance to those who take the plane out of a hangar and run up an engine once a month while the plane is not being used. To boil off the water the engine must be at operating temperature for at least 20 minutes – one hour is best. Ground running does nothing except wear the engine.
If anyone plans to not operate a plane then buy pickle oil – Shell sells it and it contains a paraffin compound which protects the inside of the engine while not being operated.
Actually the Pump warms the air up to about 35C, so it isn’t chilling the engine. So you blow warm dry air thru the engine that then draws any moisture out of the engine and is slowly over boarded as it is replaced with newer air from the pump.