More about winterizing general aviation airplanes

In the Dec. 8, 2022 issue of General Aviation News, Roger Ray outlined his pickling procedure for his aircraft to protect it during the winter when he is out of the country (A master class in how to winterize your airplane).

His procedure was quite complete, but he asked if there was anything else he could do. In reply, my friend Paul McBride, General Aviation News’ engines expert, added his comments explaining why it is so important to winterize an airplane that will sit idle for long periods of time.

I’d like to add to Paul’s comments, including my suggestions for winter oil changes.

The basis of Roger’s procedure is to change the oil before he parks his Midget Mustang to the Phillips anti-rust preservative oil. This product is qualified against the same spec as Aeroshell Fluid 2F, which may be hard to find. These products are a blend of three parts aviation mineral oil qualified to Mil-L 6082D (grade 1100) spec and one part preservative additive qualified to Mil-C-6529C.

It’s important to know that this product is blended as a straight mineral oil and not an Ashless Dispersant (AD) oil. These are considered “flyaway” oils, but should not be flown more than 50 hours for a full TBO engine life cycle.

These oils were developed during World War II to protect engines as they were exposed to the corrosive salt air as they were being shipped overseas.

The original recommendation was to idle the engine with the preservative oil in it for 15 minutes to ensure that the oil is adequately distributed throughout the engine.

If additional protection is needed, Vapor Phase Inhibitor (VPI) crystals can be added. These crystals are not added to the engine, but rather placed in a container made from screen. The container is hung in the oil fill neck and wired so that it is above the oil level. These crystals will evaporate and fill all of the air space and coat all of the unprotected metal surfaces as long as the engine is properly sealed up.

Shell used to market VPI 260 or 280 crystals, but now I believe VPI crystals are available from Cortec Corp.

I agree with Paul’s concerns about placing heat just under the engine, as Roger does with two 60-watt light bulbs.

“Having heat from the light bulbs…would cause a differential in temperature of the various engine components which, in turn, would cause the potential for moisture,” Paul noted. “This is why leaving various engine heater products on continuously does more harm than good.”

In most cases where heat is placed just under the engine and not to heat the whole engine assembly, it will cause any moisture in the oil to rise in the crankcase and condense on the cooler camshaft at the top of a Lycoming engine. This is not as critical for Continental engines because the cam in these engines is mounted below the crankshaft.

A lot of pilots have used a light or other small heater they leave on all of the time with mixed results when winterizing their airplanes.

Tanis Aircraft Products manufactures a system that heats all of the cylinders and the oil pan. It also makes a custom fit cowl blanket with proper cowl plugs. Officials with the Minnesota-based company claim that this system keeps the whole engine assembly at or above 100°F during the coldest conditions, which reduces rusting concerns.

What About Winter Oil Changes?

As far as winter oil changes go, aircraft owners should follow these guidelines:

• If you fly a normal amount in the winter, which is usually one or more times a week, and get the oil temperature up to at least 180°F, then maintain your airplane’s normal oil change interval, usually with multigrade oil.
• If you fly just once a week or so and don’t get the engine temperature up to 180°, I recommend changing the oil before you get to the inactive time and add a quart or two of the preservative oil to the oil change.
• If the plane is going to sit for a long period of time, I recommend filling the crankcase with 100% preservative oil.
• If you are in a humid climate and leave the plane sit for extended periods, hang a container of VPI in the crankcase.

Roger lives in Oregon and two 60-watt light bulbs keeps his temperature up to 50°F. However, if you live in Minnesota or any of the other states with freezing cold temperatures and wind chill temperatures that often dip below 0°, two light bulbs will not help much, which could lead to some moisture build-up on the camshaft and lifters which, ultimately, could lead to rust and corrosion.