As cold weather approaches, take steps to protect your engine

Ben Visser


Fall is officially here. That means cold weather is just around the corner.

If you live in a northern climate, you may be putting your aircraft up for the winter. If you are, there are a few steps you should take to properly protect your idle engine.

The best thing you can do for your aircraft is to put preservative oil in the crankcase before you let it sit for the winter. Approved preservative oils are qualified under the Mil-C-6529C specification. This spec was introduced many years ago to protect military piston aircraft engines that were being shipped overseas. These products are very effective at protecting all engine surfaces from rust and corrosion.

I know of only two products available that meet this specification: Phillips 66 Aviation Anti-Rust Oil and Shell's Aeroshell Fluid 2F. Not every Phillips dealer stocks the anti-rust product, but they should be able to get it. The Shell product is generally only available through the company's web site, Whichever product you use, you should plan ahead to ensure that you have it on hand by the time you plan to "pickle" your aircraft.

So how do you use preservative oil? It is very easy. Just go out and warm up your engine. This is a good time to justify a $100 hamburger. When you return, drain the oil and change the filter. Now, fill the crankcase with the preservative oil and start the engine. You need to run the engine long enough to coat all of the parts. You can fly it around the patch or just run it up on the ground. (Do not overheat the engine if you choose to do a ground run up.) Now put the plane away.

Both the Phillips and Shell products are listed as flyaway oils. That means that you can fly a small amount on the oil. However, both products are based on straight mineral oil with no cleanliness additives. I would recommend that you limit your flying to about 10 hours per oil change. Then when you change to AD oil in the spring, your engine should be cleaned up by your next oil change.

You are probably tired of everyone telling you about rust and corrosion, but they are the major causes of aircraft engines not reaching full TBO. So get used to all the talk and try preservative oil. The oil may cost a little more, but have you priced new engines lately?


You may choose to take an additional step to protect your engine. One of the problems with an idle engine is that at least one intake and one exhaust valve will be open at all times. This means that warm moist air will be drawn into the cylinder during the day and then the moisture will drop out at night, when the air is cooled down. This moisture clings to the cylinder wall and starts rusting activity above the piston rings, where the preservative oil will not protect the surface. Blocking the inlet and exhaust will help reduce this problem. You may also choose to put desiccant plugs in. Some people even put a light bulb in the engine compartment and a blanket around the cowl. All of these steps reduce the temperature variation in the engine, which in turn reduces the amount of rusting.

Check with your mechanic or engine/airframe manufacturer for any other winterization requirements for your aircraft.

Ben Visser is an aviation fuels and lubricants expert who spent 33 years with Shell Oil. He has been a private pilot since 1985. You can contact him at .

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