When the winter period comes bringing shorter days and worse weather than is enjoyed during the summer months, many owners decide to hanger their aircraft and not fly until the Spring. An integral part of the process of preparing an aircraft for storage should be to use a preservation oil to give protection against corrosion, which greatly accelerates the rate of wear in an engine.

As covered in earlier issues of the AeroShell Newsline, when an engine stands idle for long periods the oil absorbs water from the atmosphere and, combined with condensation on the internal engine components, causes rust to form. Once the rust has formed it remains in the oil and acts as a grinding paste, causing increased wear, reduced engine life and potentially higher maintenance bills.

If an aircraft is flown frequently (at least once every two weeks) then this water evaporates as the engine temperature rises and therefore does not cause a problem. However if the aircraft is not flown as often as this, then the owner should consider using a preservation oil.

Shell produce such an oil AeroShell 2XN, which can be used neat for long term engine inhibition, or blended in the ratio of one part of AeroShell Fluid 2XN to three parts of fresh AeroShell Oil 100 (straight oil) to be used as an inhibited flyaway oil - and we'll come back to this point in a moment. This resulting mix is excellent for use in engines that are going to be inactive for several months as is often the case over the winter months.

This blend of AeroShell Fluid 2XN and AeroShell Oil 100 can be used in any certified aviation engine, although we don't recommend its use in 2 stroke or automotive derived engines.

As mentioned, once mixed with fresh AeroShell Oil 100, this oil can be used as a flyaway oil. This means that unlike some preservation oils it can be used as an operational oil in most engines (large radials excepted) for up to a maximum of 50 hours during the TBO cycle. Note that this is 50 hours during the total TBO cycle, not 50 hours every time you use the oil.

This means that if you want to fly then you still can without needing to drain the oil and replace it with your usual AeroShell grade; but remember that this oil is a 100 weight oil and so if the temperature is too low for this weight of oil in your engine then the oil should be preheated. Extensive flying on this oil will not harm the engine, but engine cleanliness may be effected as the preservation oil does not contain an ashless dispersant additive as the AeroShell W series of oils do.

So how is it used?

Once the AeroShell Fluid 2XN has been mixed with AeroShell Oil 100, your normal operational oil can be drained and replaced with this blend. Run the engine for about 15 minutes - either on the ground or in the air - to circulate the oil. Shut the engine down and follow your normal storage procedure.

For additional protection, this oil can also be sprayed into the cylinders and other areas. Once the engine has cooled, it is also worth blanking off the intake and exhaust if possible to reduce the flow of air (and therefore moisture) through the engine. However remember to placard the cockpit to remind yourself and other pilots that this has been done.

Once you are ready to change back to your normal oil, pull the propeller through several times, drain the preservation oil and refill with the correct grade of aviation oil.

Many of you with low utilisation aircraft are currently taking advantage of the anti wear and anti corrosion additives in our AeroShell Oil W 15W-50 multigrade, and you may be wondering whether or not to use a dedicated inhibiting oil such as AeroShell Fluid 2XN. The answer lies in the utilisation of your aircraft.

If you intend to carry on flying throughout the year, but may have a few periods of several weeks inactivity, then use the AeroShell Oil W 15W-50. However if you intend to lay the aircraft up for several months (winter or summer) and perhaps enjoy the occasional flight during this period, then you should use AeroShell Fluid 2XN mixed with AeroShell Oil 100. Finally, if you have an engine which will lie idle for an indefinite period, such as a spare engine, then you should use AeroShell Fluid 2XN in its pure form.

By using these simple solutions, no matter how often you fly, you can be sure that you are giving your engine the best protection possible.