Hello to my subscribers, new readers, and all aircraft and restoration lovers. My name is Greg and this is my second instructable.
I work at an aircraft scrapyard. I'm a pilot, and flight instructor. I love planes, motorcycles, and electronic goodies.

Today we're going to change the oil and filter on a Cessna 150.
The Cessna 150 is probably the second most popular aircraft in the world, right behind the Cessna 172.

If you have a Cessna and you'd like to save a little money, doing your own oil changes is a good way to do it.

Step 1: What Tools You'll Need

The tools you'll need for a Cessna 150 are:

Phillips no. 2
Adjustable Wrench (Monkey)
Side cutters, or wire cutters
Lock wire pliers suggested
1 " wrench suggested
5/8 " wrench (custom)

Most other light aircraft will be similar, except newer planes don't have an oil screen.

Changing the oil in your airplane is considered "elementary maintenance" which means any competent person should be able to perform this work, assuming they are doing it under the supervision of the owner or an AME (aviation mechanical engineer).

Step 2: Remove the Engine Cowls

The cowls on most cessnas are in 2 pieces, top half and bottom half. You just unscrew all the fasteners and carefully lift the top off.
Note: the fasteners are zeus quick release screws. They only rotate a quarter turn and then they are loose.

The bottom cowl is a little trickier, when you loosen one side the cowl will flex and try to fall off and could be damaged. So , loosen all the bottom screws but leave one screw on each side until you're ready, then hold the bottom with your hand or your knee and remove the remaining fasteners.

I like to make sure the propeller is horizontal before doing this. Make sure the mags are off before turning an aircraft propeller.
Make sure you put the cowls down in a way the wind won't pick them up and run off with them.

Step 3: Drain the Oil

The oil drain on this particular engine is a quick drain spout. Anytime you apply upward pressure on the collar a ball bearing is pushed out of the way and the oil will drain out the bottom. We use a hose to allow the oil to be directed into an oil catch bucket.
(the oil will flow faster if the engine is warm)

Step 4: Remove the Oil Filter

The oil filter is standard, but it is lock wired into position so you will have to cut and unravel the lock wire to be able to remove the filter. It will have some oil in it so be ready to dump it into the oil catch bucket.

Step 5: Remove the Oil Screen

The oil screen is a "feature" included on some aircraft to show pieces of metal flaking off your engine over time. We still use ours and check it and this is how you do it.

The oil pressure probe is installed in the middle of the screen, and it is removed first using our custom 5/8" wrench. Slide the wrench over the wire and then loosen the probe until it can be pulled free. Sorry for the pictures, there isn't much room and my assistant was MIA.

Next, use your adjustable wrench to slowly and carefully undo the oil screen nut. It's the big square one.

There is your oil screen.

Step 6: Inspect the Screen and Filter

Here you're looking at the screen to see if there are any shiny or reflective pieces of metal. If there are then you can track how ma ny accumulate over time and it's one of many ways you can communicate with your engine to see when it's going to go for a walk on you.

The little lumps of black are carbon pieces and usually are a non issue. We clean them off the screen after inspection and reinstall.

To inspect your oil filter you can cut it open with a hack saw and run a magnet in all the folds of paper to see if there is metal particles.
Always use a new oil filter when doing an oil change.

Step 7: Reinstall Screen and Lock Wire

Reinstall the oil screen in the opposite order of installation. Unfortunately I haven't been able to do this job without our custom 5/8" wrench.

Lock wire is a little fancy, You should have someone show you how to do it if you've never done it before.
I'll try to give a demo of lockwire in the future.

Basically, you have to loop safety wire around parts that you don't want to vibrate loose. Then you spin the lock wire until all the slack is taken up, and tighten it onto somewhere on the engine or frame so that the part can't budge. It takes some practice, and even if you think you have it it's probably still too loose, so I recommend getting a friend or your AME (Aviation Maintenance Engineer) to demonstrate it before you trust your life to it.

Step 8: Reinstall Filter and Lock Wire

Reinstall the oil filter in the opposite order of installation. The oil filter can go on hand tight just like on your car, when the engine heats up it will seal on tight.

Make sure you lock wire this piece tightly as it isn't on that tightly in the first place. I find the filter is easier to lock wire since there is much more room.

Step 9: Fill Up With Oil

Remove the drain hose from the oil pan and make sure you pop the collar down on the drain plug. Then the plane is ready for new oil. I suggest you pour in one quart and then check for leaks around the oil pan plug and screen. You won't be able to see any leaks around the filter until the engine is full of oil.

Make sure you use the correct amount of oil for your engine. This one uses 6 quarts, but is generally happy around 5 quarts. Bigger , higher power engines need more oil. Constant speed propeller engines need more oil.

The grade of oil you use depends on which motor you use and what temperatures you will operate the aircraft through. Also, if you have a new engine or have completed certain engine maintenance, then you might need special mineral oil. Only use oil approved by your engine manufacturer or AME.

Step 10: Test Run the Engine

Now that you have filled the engine with oil, put on the oil fill cap again and check again for leaks. Everything should be ready for a test run. Move the aircraft to a safe location and start it up and let it idle for a few minutes. If there are any abnormal engine readings or sounds different than before, immediately shut it down and inspect it. If all seems well after 5 minutes, shut down the engine, check for leaks, dip the oil level and confirm it is in the correct range.

If all really IS well, then proceed to the next step.

Step 11: Reinstall Engine Cowlings

If you made it this far,
Good Job!

The oil change is almost done and you just saved yourself a hundred bucks or more.

Bottom cowl first, slide the cowling roughly into place and tighten one fastener on one side, then one on the other. Make sure the cowl is lined up properly and in position then tighten the rest of the fasteners.

Then lay the top cowl on top of the engine and tighten one fastener on each side. Make sure it is in place correctly and lined up the way it should, then tighten the remaining fasteners.

Ensure the ignition is off and turn over the prop to ensure the cowling is not binding on the propeller.

Make an entry in the aircraft journey log, and the engine technical log, stating that you changed the oil on today's date, with the amount of oil you added to the engine and the type of oil and filter you used.

Make sure you check all the fasteners twice. It's easy to forget one.

Step 12: Oil Change Complete

This aircraft is ready to fly another 25 hours before it is due for another oil change and inspection.

Thank you! Please raise your hand with comments and questions.

WARNING:
Do not attempt maintenance of an aircraft unless the work in question is by definition "elementary maintenance" and you are the owner or are supervised by the owner of the aircraft. Do not attempt maintenance other than elementary maintenance unless the aircraft is in the "Owner maintenance category" and you deem yourself up to the task and you are the owner or are supervised by the owner of the aircraft. Do not modify an aircraft unless the aircraft is a homebuilt or kit aircraft and you are the owner or are supervised by the owner of the aircraft.

WARNING:
Do not go flying unless qualified under the licensing standards for your country/state/province. Do not fly in an aircraft unless it is properly maintained according to manufacturer and country standards. Do not fly an aircraft unless you are trained on the type and class you intend to fly. Do not fly an aircraft unless you are current on the type and class you intend to fly. Do not fly an aircraft in any weather or conditions you are not qualified for. Do not fly an aircraft in any weather or conditions the aircraft is not manufactured to withstand.