Changing the oil is one of the most important things the owner of any engine can do to ensure the health and longevity of the machine he relies on. The FAA allows aircraft owners to perform this task without mechanic supervision as part of the owner maintenance regulations in FAR Part 43. With that said, the first time this procedure is performed, it is strongly recommended that an experienced person supervises to ensure that the change is performed correctly.

The Continental A-65 is a simple, reliable engine that’s powered light aircraft for over 80 years. It comes equipped with a removable, reusable oil screen, rather than a spin-on filter like most modern car (and aircraft) engines. Continental recommends changing the oil every 25 hours, or 4 months, on engines with reusable screens.

Oil brand selection is subjective, but Continental recommends the use of 20wt or below in temperatures below 40ºF, and 40wt above that temperature. As a result, many owners use a multi-weight oil to remove the need for oil changes between seasons, with 20w50 being a popular choice.

The tools required for this task are the following:

• 3/4″ pipe wrench
• 3/8″ flare nut wrench
• 7/8″ wrench
• 4 qt. oil
• Safety wire
• Wire cutters
• Oil drain pan
• AN900-28 (MS35769-48) crush gasket (for screen)
• AN900-10 (MS35769-11) crush gasket (for drain plug)
• Safety wire twister pliers (recommended)

The oil change should be performed while the engine is at operating temperature, to ensure that wear particles are in suspension when it is drained out of the sump. It is recommended by Continental that an oil analysis be performed at each change, in order to monitor wear trends from one change to the next.

The first step to the oil change is the draining of the old oil. A safety wire is present connecting the drain plug to the bottom of the oil sump, and that wire will need to be cut in order to remove the plug. Once the wire has been cut, a wrench can be used to loosen and remove the drain plug. With the drain pan positioned under the engine, about 3 quarts should end up coming out. If an oil analysis is going to be performed, the sample should be collected mid-stream.

While the oil is draining, the next step, removing the oil screen, can be performed. Before the screen is removed, the temperature probe must be removed from the screen housing. The temperature probe is relatively fragile, and care should be taken when loosening and removing it, including the use of a flare nut, rather than open ended wrench.

With the probe pulled out of the screen housing, the screen itself can now be removed. Similar to the plug, safety wire is used to connect the screen to the rest of the engine, generally to the tach cable adapter. This wire needs to be cut for the screen to be removed. With the wire gone, a pipe wrench can be used to loosen the screen, and it can then be spun off by hand. Oil will come out of both the screen and the engine, so a drain pan underneath can help to avoid a mess.

With the screen removed, it needs to be checked for particles. This is the primary way of detecting excessive engine wear and will provide more accurate results than any other detection method, including oil analyses. Metal particles are indicators of wear, and if noticed, should be reported to a mechanic immediately to root cause the issue. The screen also needs to be cleaned – avgas can be used for this, or mineral spirits. Swishing the screen in one of these in a clean bucket will clean the screen and make it easier to analyze any particles that fall out. A magnet is also helpful to determine if a given particle is iron/steel or something else, like carbon buildup.

Once the screen is cleaned and checked for particles, re-assembly can begin. A new crush washer should be used, with the seam facing the accessory case. The screen can then be spun back into the accessory housing; once hand tight, the pipe wrench can be used to tighten the screen back on. Once tightened, it should be re-safetied, and the temperature probe re-inserted and tightened.

With the screen re-installed, the drain plug should be put back on the sump, along with a new crush washer; the seam of the gasket should be facing the sump. Once hand tightened and tightened with a couple turns of a wrench, the plug should be re-safetied.

With the screen and plug re-installed, the sump should be re-filled through the dipstick/filler neck. The best way to know how much oil to add is to measure how much was emptied, but starting with 3 quarts and then checking the level will also work.

At this point, the oil has been successfully changed, the screen has been cleaned and inspected, and a logbook entry needs to be made to record the event. For specific details on how to format the logbook entry if written by a non-mechanic, see FAR Part 43.