In my last column I talked about the use of the preservative oil, Aeroshell 2F, to prevent rust in idle engines. I have since learned that Shell is phasing 2F out and in the future will only offer Aeroshell 2XN.
Before you panic, let me explain. 2XN is just the additive system out of 2F. To make the exact 2F, you would blend three parts Aeroshell 100 mineral oil and one part 2XN.
So if you want to have the same protection for winter storage and would normally just add a quart of preservative oil to the oil change, now you would just add one quarter of a quart of 2XN to the change.
If you are going to store an engine for a longer period, especially in wetter climates, then you can add two quarts of 2XN to an eight-quart oil change, which would be the same treatment level as straight 2F.
The advantage of 2XN is that you need less volume and you can add it to the normal oil, usually an AD oil, you use.
If you would like more information on this product you can contact Shell on its website at Shell.com/Business-Customers/Aviation/Aeroshell
To Crank or Not to Crank?
I received an interesting question from a pilot who was going to recover a fabric-covered aircraft. He had removed the engine and had it in the shop on a stand. The question was whether to use the starter to crank the engine over until they get oil pressure every month or so. The theory is that the cranking would coat all of the parts with a fresh coating of oil and keep rust down. They are also doing the desiccant plugs and sealing all of the openings to the atmosphere.
My first suggestion was to add some 2XN in the oil and crank to mix the additive into the oil. (Phillips also offers a preservative oil that meets the same spec as Aeroshell 2F).
The debate on whether to crank or not has been around for many years. You all should know that just starting an engine on the wing during storage is not a good thing. The problem is that when you hit the primer, you pump raw fuel into the intake. When the engine does start, some of the fuel ends up in the crankcase, where it mixes with the moisture in the oil to form acids that actually increase the rust and corrosion in the engine. So if you start it up, go fly it until you get the oil temperature up to get rid of the moisture that has accumulated from sitting.
But this pilot only plans to crank the engine. The problem here is that the highest lubricated load point in an engine is the cam and flat tappet interface. This means that this area is the most vulnerable to rust, which can lead to pitting and eventual failure. Therefore, this is the most critical part of the engine that needs protection during storage.
In a Lycoming engine, the camshaft is located above the crankshaft at the top of the engine. When they crank the engine until they get oil pressure, oil is pumped into the lifter galleys and cam bearings, but not directly onto the cam/lifter interface.
When you first start cranking an engine, the first few turns cause much of the cam wear and I am not sure that when cranking the engine one would get oil splashed onto all of the cam lobes and tappet faces. I guess it would depend on how long you crank the engine.
I have talked to several old timers about this, and several of them claim the best way to store a Lycoming engine is upside down, after a fresh oil change, so that the cam and lifters are covered with oil.
Others have claimed that filling the crankcase completely full works the best.
I think I would go with the preservative oil, spray the cylinders, use desiccant plugs, and store it upside down. Then do not crank it, but check all cylinders for oil before starting it when the plane is done.