Q: There was a company that made engine pre-oilers. This would be the perfect component to add to an aircraft engine, wouldn’t it? You could go out to your hangar and turn on the pump, circulating oil over all those areas that suffer from corrosion. Why aren’t these more popular?
Rolf Ringgold
A: Rolf, you’ve raised an interesting question and I am probably opening a can of worms by answering it.
Engine pre-oilers have been around for many years and, if I’m remembering correctly, they were very commonplace during the big radial engine days.
It really depends on whether you are buying or selling them as to their usefulness and it’s at this point I could get myself in trouble.
I’ll share with you my personal thoughts. There is no doubt they serve the engine well when it comes to getting oil to certain areas of the engine.
However, the pre-oilers I am aware of do nothing to provide oil to the most critical areas, especially when it comes to corrosion, such as the interface between the camshaft lobe and the tappet body face, and the cylinder walls.
While these areas are the most critical when it comes to potential corrosion, they have no pressure oil feeds like the main, connecting rod, and camshaft bearings have. The corrosion prone areas I’ve mentioned are only lubricated with splash oil after the engine is started.
This raises the question as to whether the pre-oilers really serve the purpose we think they should.
While they certainly don’t cause any problems in the engine, they are incapable of doing what we’d like them to do, which is provide oil to those areas where we know there are serious issues, especially if an aircraft has extended periods of inactivity.
The best method to prevent corrosion in your engine is to fly it frequently for long enough to get the oil temperature up to at least 180°F for a half hour before landing.
Under no circumstances should you just ground run the aircraft. That is not a substitute for flying and, in fact, adds insult to injury by generating more condensation in the engine, which leads to corrosion.
Also important is to do frequent oil and filter changes (25 hours with a pressure screen or 50 hours with a full flow filter) and go no more than four calendar months.
The issue is not the lubricating factor of the engine oils, but rather getting all of the contaminates from combustion and condensation out of the engine. Those are what accelerate corrosion. By following an oil change schedule you can keep corrosion from getting its foot in the door.
Remember engine oil is one of the least expensive things you can put in your engine.
Dry your engine out. Buy a cheap low pressure air pump that draws near zero humidity from your hangar fridge and blows it into your engine. My rudimentary Testing has shown that this air, lighter than blowing on your hand, will take an engine from nearly 99%RH after a flight to less than 10%RH in 20 minutes. It gives you a nearly bottomless supply of desert dry air for the 98%+ time that you aren’t flying.
And add CamGuard at every oil change. Oil analysis results will improve. I think it helps to avoid cold starts (preheat below 40dF) and keep the RPM below 1,000 until the oil warms somewhat. No takeoffs until oil temp reaches 100dF.
Works for me for the past 19 years on the same Continental engine that was born six years before I bought the airplane (CamGuard since 2008).
Someone smarter than me said, “It’s not how hard you run the engine, it’s how you run it hard.” Thank you, George Braly.
Our ’61 Continental GO-300 has used Camguard, 20w-50 multi weight oil and a spin-on oil filter for 10 years.
The oil pressure cones up in seconds, and I wait in the run up area until I see 90 degF oil temp, [ the needle comes off the peg ], before doing the run up.
When we first started using Camgurad the oil filter had a large amount of small carbon bits. I found that Camguard scavenges carbon from the cylinders and ring lands.
I would thing that preheating the oil to 100 degF would be more helpful than pre-oiling..?
I agree completely. There was a Cessna 140 tied down next to my Cherokee for years. The owner would come out 2 or 3 times a year with 2 gallons of fuel and run the engine on the ground until the fuel was used up. A friend eventually bought the plane and discovered massive corrosion throughout the motor, cam, lifters, crank, everything. I’d rather see a guy come out and pull the prop through a few times every month or so than run the engine for an insufficient period of time to burn out the moisture. It also adds combustion by products into the oil.