There are two things you can do that will extend the life of your engine more than any others: fly your airplane regularly and change your oil as specified by your engine’s manufacturer. There are other things you can do to help or hurt your engine to be sure, but if you made two big piles, one with engines killed by infrequent flight and lack of oil changes and the other with engines destroyed by all other causes, it wouldn’t even be close. So go fly! And change your oil every four months or 50 hours if you have an oil filter, and every 25 hours if you don’t.
This special tool allows you to drain your oil filter before you remove it. The clamp tightens around the filter and the pin is driven through the filter can, allowing oil to drain out the tube.
Step-by-Step Oil Change
Changing your oil is a fairly simple process, but like anything else there are better and worse ways to do it. Here are the basic steps for a Lycoming engine:
1. Warm the engine up to operating temperature. (There’s that “go fly” thing again.)
2. Drain the engine oil into an appropriate container, one that you can use to recycle the used oil.
3. Retrieve a small sample of oil from the stream of draining oil to send in for oil analysis.
4. Give the engine a chance to completely drain before you shut off the quick-drain or reinsert the drain plug.
5. If you don’t have a quick-drain valve on your engine sump, now is a good time to install one. They run about $79 for a Lycoming engine or $39 for a Rotax, and they are definitely worth it.
Use a one-inch wrench to remove the oil filter from your Lycoming. If the filter will not yield, some large water pump pliers may work better.
A quick-drain valve replaces the standard sump drain plug and makes oil changes so much easier. Install one at your first opportunity.
Be sure to take an oil sample from mid-stream as the oil drains out. Oil analysis can provide a valuable early warning of many engine problems.
Oil needs to be drained into a suitable container and recycled. Most airports have oil recycling stations for your use. Be sure not to contaminate the oil with other chemicals or avgas.
6. Remove the oil filter and save it for examination later. Begin by loosening the filter with an oil filter wrench or a one-inch combination wrench. In some cases a large pair of water pump pliers may be needed to break the filter loose. Once the filter is loose enough to turn by hand, place a plastic bag around it to catch oil draining from the filter and unscrew the filter. There is also a special tool you can buy to remove oil from the filter before loosening it. I never bought one because they cost over $100. Be sure to have a few rags or paper towels handy to deal with the inevitable mess.
If your engine does not have an oil filter, you should consider adding one. Your wallet will suffer to the tune of $300 to $400, but a new engine is so much more.
7. Drain any remaining oil from the filter and take it over to your workbench to cut open and examine. Oil filter cutters begin at around $60. Airwolf makes a pretty good one for about $88. This is a “must-have” tool for any Experimental airplane owner.
An Airwolf oil filter cutter makes quick work of opening up this used oil filter.
Once the oil filter has been cut open, remove the filter media for examination. Be sure not to introduce foreign material into the media.
8. Secure the oil filter in a vise and use the cutter to remove the bottom (part that goes next to the engine) from the filter can. Set the can bottom aside and remove the filter media, being careful not to contaminate it with any foreign material such as filter can cutting remnants.
Cut the media loose from its holder using a serrated steak knife or a utility knife.
Remove the media from the holder and open it up to check for metal.
9. Place the media in a clean pan or tray and cut the media (folded paper) loose from the core. Use some side-cutting pliers to remove the metal clip that holds the paper media together, and then use a filter media cutter or just a plain old utility knife to separate the media from its metal end plates.
10. Once the media is cut loose, open up the folds and look for trapped particles. You should expect to see a few and hope not to see a lot.
A few small flakes of aluminum turned up in this filter. This small amount is of no concern, but the quantity and type should be noted for future reference.
A few small specks of carbon also turned up in this filter, but again the tiny quantity of material present is of no particular concern at this time.
11. If there is anything more than a small amount of metal found in the filter media, you should also remove the sump screen and look for larger metal pieces. Lycoming recommends that you inspect the sump screen at every oil change, but at a minimum you should check it once a year no matter what, and whenever any significant metal is found in the filter.
12. Assuming there are no unpleasant surprises in your oil filter or sump screen, write your tail number, tach time, and date on a new oil filter with an indelible marker and install it on the engine. Place some grease such as Dow Corning DC-4 on the threads and tighten the filter to 17 foot-pounds. Then safety-wire it to keep it secure. Don’t forget to replace and safety-wire the sump screen, too, if you removed it.
13. Refill the crankcase with aviation oil approved for your engine and operating conditions. Usually a quart below the maximum is plenty.
It is best to use an oil filter torque wrench to install your oil filter. This one made by Champion is preset to 17 ft. lbs.
The author writes the tail number, tachometer hours, and date on the new oil filter before installing it. Be sure to use an indelible marker such as a Sharpie for this.
Oil Analysis
Oil analysis is another important tool for monitoring the health of your engine. Take a sample from mid-stream when you drain your oil, being careful not to let any foreign material fall into the sample jar. Always use a clean jar as provided by the oil analysis lab. Oil analysis works best over time where you can note trends and changes. A single oil analysis is not all that useful unless there is a large problem that is probably already obvious from material in your filter and/or sump screen. Set up a file system to track your results over time, and try to stick with the same lab for greater consistency. Lycoming Service Letter L171 goes into greater detail on oil analysis. It is available online.
Lycoming suggests inspecting the sump screen at every oil change. At a minimum you should check it at every annual inspection and whenever any metal of a large size or quantity appears in your oil filter.
What Oil Should I Use?
When selecting an oil for your aircraft, stick with products by the major aviation oil manufacturers such as AeroShell or Phillips. Aircraft engines have very specific lubrication needs that are not well served by oils not specifically designed for aircraft. After that, the answer depends on the operating conditions you will be likely to encounter, especially temperature. Phillips recommends their X/C 20W-50 oil for all standard conditions except when dealing with Lycoming 76 series engines (O-320-H2AD, etc.) AeroShell recommends their multi-viscosity 15W-50 oil for all standard uses, but also sells single-grade 100W for use above 60 degrees F. The 100W oil has the benefit of being less expensive and is fully compatible with the 15W-50 oil. By the way, it is fine to use Aeroshell 100W in the summer and then switch to 15W-50 in the winter. You can save a bit of money and be no worse off for it.
With any engine, the first time you start it up under power after an oil change, you should check for leaks and be sure you quickly establish a safe oil pressure. Leaks and low oil pressure are problems you need to find while you are still on the ground. If everything looks good, close up the cowl and go fly.
When you cut your filter open, there are four types of particles that you may find. Black particles that can be broken up are carbon particles. They are common and of no great concern, especially with engines that burn a lot of oil, unless they are excessive. Excessive means more than a quarter teaspoon or about enough to cover your thumbnail. Expect to find a few of these in most filters.
Copper-colored particles are brass or bronze, most commonly from valve guides, but in some cases from wrist pin plugs. Excessive valve guide wear is troubling, so more than a tiny bit of gold material in the filter should prompt you to look for the source.
Silver or gray particles that stick to a magnet are steel or cast iron. Likely sources of magnetic material include lifter faces and camshaft lobes, oil pump gears, or piston rings. Obviously the more of this material you find, the less happy you will be, but a small amount is no reason to hit the panic button. However, any large pieces that exceed the size of a broken pencil lead are cause for concern and should move you to remove the sump screen and look for bigger chunks. Unfortunately, the most likely source of ferrous metal in your filter is a failing cam and/or lifters.
Silver or gray particles that are not magnetic are most likely aluminum, but could also be bearing material. Shiny aluminum particles are pretty common and not particularly troubling in small quantities. These are often shed off the aluminum wrist pin plugs found on most Lycoming engines, although they can also be shed by pistons. Dull gray flakes can be bearing material, a troubling sign to be sure, but one that should also be showing up as lower oil pressure and possibly elevated oil temperature.
The key to your level of concern is the quantity and the change in amount from the last oil change. A sudden increase in the amount of material in your filter is a sign of trouble, as is any large quantity. Any pieces larger than a broken pencil lead also point to more serious problems that need immediate attention.
New engines or freshly overhauled ones will initially make more metal as they break in. This is normal. Once an engine breaks in, and certainly after 100 hours, you should expect to see very little metal in your oil filter. However, very little metal is not the same as none. Do not panic the first time you see a tiny flake of aluminum in your oil filter. As an engine develops problems, more metal will likely appear again, long before a catastrophic failure. Pay attention to the early warning signs and keep yourself safe. If you have any doubts, contact a good mechanic or call your engine manufacturer’s technical support staff. They can help you decide when to take further action to track down the source of metal in your filter.
Lycoming has a more detailed description of what you should do when you find a small amount of metal in your oil filter. It is sort of hidden in Service Instruction 1492D dealing with piston pin plug wear. This service instruction is available online at www.lycoming.com. It is worth reading the whole thing, but this is a quick summary. They make recommendations on the basis of the size and quantity of metal (magnetic or non-magnetic) found in the oil filter. They define small as 1/16-inch diameter or less.
Below is a quick survey of what you might find in your oil filter. It should not be regarded as the last word on oil filter analysis, but rather serve as a starting point for learning about this process. Every aircraft engine has its own unique set of operating history and conditions that must be considered, in addition to whatever information an oil filter examination might reveal. In all cases where there is any doubt, seek out expert help to evaluate your individual situation before further flight or any major teardown is considered. Another good source of information on this topic is an article that appeared in the October 2013 issue of Light Plane Maintenance. This publication is geared towards A&P mechanics, but often contains information that is valuable to Experimental aircraft owners and mechanics, too.
—D.P.
The Rotax engine has a very different oil change procedure than a Lycoming or Continental engine. Used oil drains out of the remote oil tank on the right.
Rotax engines will need a different approach to oil changes due to their dry sump design, in which the oil is stored in a remote tank rather than the engine’s crankcase, and other design differences. Rotax engines prefer to run on unleaded gasoline but will also run on 100LL avgas. Unfortunately, you must change the oil twice as often if you run avgas 30% of the time or more. This means that the standard 50 hour oil change interval gets shortened to 25 hours with avgas. Here is the oil change process for the Rotax 912 series and 914 engines:
1. Warm the engine up to operating temperature and remove the cap from the oil tank.
2. Be sure the ignition system is off.
3. Turn the engine over by hand in its normal direction of rotation. As you do, listen for the telltale “burp” as the last of the oil is pumped from the crankcase into the oil tank.
This drawing from the Rotax maintenance manual shows how much metal is acceptable on the magnetic drain plug. Too much metal means a teardown is required before further flight.
4. Remove the drain screw from the bottom of the oil tank and drain the oil into a proper container, taking a midstream sample for oil analysis as you do. Do not move the prop or break any oil lines loose while the oil tank is empty. If you do, you will likely need to go through a much more involved priming process as described in the Rotax maintenance manual.
5. After all of the oil has drained from the tank, replace the drain screw with a new washer, torque it to 18 foot-pounds and safety-wire it in place. Refill the tank with the prescribed amount (about 3 quarts) of approved oil. Note that this will not be standard aviation oil, but oil especially formulated for the Rotax engine such as AeroShell Oil Sport Plus 4. This oil is designed to work with the gear reduction units and clutches that are integral parts of Rotax engines. Many Rotax owners use high-quality motorcycle oils instead of the Aeroshell product, but it is vitally important that any oil used has a gear additive to handle the loads of the gear reduction drive in the Rotax engine. The main point to be made is that standard aviation oils such as Aeroshell 15W-50 or Phillips 20W-50 are not acceptable in Rotax engines.
6. Remove and save the oil filter for later inspection and replace it with an approved part. You will need a strap-type oil filter wrench to do this properly. Lycoming oil filter wrenches will not work.
7. Install a new oil filter by first lightly oiling the gasket and then screwing the filter on until it is solidly seated. Then add ¾ turn to achieve its final tightness.
8. Remove the magnetic plug on the engine crankcase below cylinder #2 and look for metal filings. There should be few to none present. This metal most likely comes from the gears in the propeller drive. An excessive amount of metal on the magnetic plug is cause for repair or overhaul before further flight.
9. Oil filter inspection with a Rotax is similar to that for a Lycoming, but as a general rule, you should expect to see much less metal in the filter due to differences in the designs of these engines. After break-in there should be almost no metal present in the filter. The ¼ teaspoon that Lycoming finds acceptable would be cause for an immediate teardown of a Rotax engine. Again, you are looking for total quantity, and more importantly, any change in quantity or type from the previous oil change. If in doubt seek qualified help to assist in your evaluation of your filter material.
10. With the new oil and filter now in place, turn the engine over by hand for at least 20 turns to ensure that you have purged all the air from the oil system. This can be done with the starter motor if your ignition system is set up so that you can activate the starter with the ignition system off. Do not start the engine until you are sure oil is circulating properly. If you have inadvertently opened up the oil system during the oil change process, please refer to the oil system priming procedure in the Rotax maintenance manual before attempting to start the engine.
—D.P.
Dave Prizio is a Southern California native who has been plying the skies of the L.A. basin and beyond since 1973. Born into a family of builders, it was only natural that he would make his living as a contractor and spend his leisure time building airplanes. He has so far completed three—a GlaStar, a Glasair Sportsman, and a Texas Sport Cub—and he is helping a friend build a fourth, an RV-8. When he isn’t building something, he likes to share his love of aviation with others by flying Young Eagles or volunteering as an EAA Technical Counselor. He is also a member of the EAA Homebuilt Aircraft Council.
Please tell me where I can get the special oil drain tool that you talked about in this article.
“Changing your oil.” By Dave Prizio -January 20, 2014 (https:/ /www.kitplanes.com/maintenance-matters-13/)
The tool is the yellow one that pierces the can and drains out the oil via an attached tube.