Ask Paul: Does my engine need an oil filter?

Q: I just purchased a 1978 Citabria 7ECA with a Lycoming O-235-C1. Just had my first oil change done — it has no oil filter! Just one, maybe two, screens.  Are these screens just as effective if I change my oil every 25 hours?  Should I add an oil filter? Is that even possible?  I run Phillips X/C and CamGuard. Your thoughts?

Jimmy Schramm, Tampa, Fla.

A: Jimmy, the question you’ve asked is a common one and not only applies to your O-235-C1, but to most all Lycoming engines. The answer to the question can you add an oil filter is yes, you can, providing you have the space between the engine and the firewall.

However, I would not add an oil filter to the engine if the aircraft were mine, so the answer to this question is no.

The reason I wouldn’t do it is quite simple, using your situation as an example.

First, I wouldn’t spend the money, and second, with you changing your oil every 25 hours, it’s easy to keep tabs on the engine health as far as detecting any telltale signs of wear taking place inside your engine.

The important thing here is to be certain to remove, inspect, and clean the oil pressure screen every time you change your oil. You should also remove, inspect, and clean the oil sump suction screen located in the engine oil sump. This oil suction screen is not as fine as the oil pressure screen, but will collect larger pieces of contaminates, such as pieces of carbon, etc.

I’d like to recommend that you continue to change your oil every 25 operating hours, but also do it every four months as well.

The reasoning behind this is that you are removing the contaminates from the oil, which are by-products of combustion and moisture. It’s these things that cause internal engine problems over time if the oil is not changed on a regular basis.

I’d recommend you ask your maintenance facility to let you look at or give you a copy of Lycoming Service Bulletin 480E, which addresses the subject of oil and filter changes and screen cleaning.

I think because you live in a rather warm climate, you probably don’t get as much moisture in your oil as an aircraft based in a cold climate or where the engine sees radical changes in outside air temperatures in relationship to the internal engine temperatures, but I’d still feel following the 25-hour and four-month recommendation would serve your engine best.

While many people will argue that the oil is still good — and I wouldn’t argue that point — it’s the contaminates in the oil that I want removed from the engine because it’s those that cause the internal corrosion that we don’t want if the oil is allowed to remain in the engine for long periods of time.

I’ve tried to get the message across to aircraft owners, pilots, and anyone who would listen that the two least expensive things you can put in your engine are fuel and oil. Translating that into simple language means change the oil frequently according to Lycoming Service Bulletin 480E or its latest revision and don’t lean the fuel mixture aggressively.


  1. Mack says

    I run in a hot climate, my preference is an oil that has high-temp lubricity, an oil that maintains it’s film strength at high oil temps.

    That makes the semi-synthetics, my choice.

    Particulates, debris in the oil, can make the lubrication more abrasive. For that reason, I have an oil filter, a filter that blocks particulates and carbon, and a filter that pulls any magnetic debris out of circulation, too. Ground-up iron is destructive to rotating parts.

    As far as moisture, I let it evaporate out of the dipstick/oil fill hole after every flight. When the engine cools, the moisture is gone, not inside the crankcase, anymore.

    • says

      Consider an oil analysis test at some engine time SMOH. 8 materials used with engine parts are shown as wear result values. An analysis data of the “same” engine model with similar engine hours and oil hours. As an A&P/IA, I recommend the oil analysis to aircraft owners. And what maintenance shows in the engine logbook. Yes for an oil filter, split the filter open, some chunks can be found that the screens pass through. OK? note owner. Only the A&P sign off returns the aircraft to service.

  2. Dennis Reiley says

    I have to disagree with Paul, every internal combustion engine needs an oil filter – even those that have frequent oil changes. An oil filter can mean the difference between getting to your destination safely and experiencing a catastrophic engine failure. Lycoming needs to do some testing on oil change intervals using an oil filter – as does every aircraft powerplant manufacturer. Operating an aircraft is expensive enough and costs need to be reduced. The aircraft industry is a good fifty years behind the automotive industry. Just because your grandpappy did it that way is not a good reason for you to do it that way.

  3. Charlie Masters says

    Your comment “two least expensive things you can put in your engine are fuel and oil” is one of those old adages that the Lycoming reps have on their stone tablets. They do not authorize lean of peak and use this phrase. Maybe when gas was $1 a gallon and oil was $1.50 per quart this was true. Maybe it still is but only because a 180 hp engine built with 1940’s technology cost more than a car, with its engine, transmission, tires, brakes, electric windows, stereo, wifi and air conditioning. $6 a gallon gas and $10 a quart oil means some of that calculus must change.

  4. C Flatt says

    One can ask this question to a thousand different people and get a thousand different answers. Just like any other question that is asked about aviation. It comes down to personal preference. I have a oil filter on any engine I have that has a crankcase. It makes me feel better knowing I don’t have the particulates floating around. So I installed an oil filter on my airplane, and I change my oil frequently also, so I get the best of both. It comes down to what you want and what makes you feel better about your airplane. I like an oil filter, so I use one.

  5. Hugh says

    I change the oil on our Cherokee 180 every 25 hours. I’ll let it go over but never exceed 50 hours. This plane fly’s every week and has a filter. We use Aeroshell W15W50 it’s semisynthetic, to me that means nonsynthetic so 25 is my interval. In my Ercoupe with no filter I use Aeroshell W 100. The airplane ran with straight weight 50 for 68 years and 2700 flight hours on the same engine; the engine now needs overhaul but runs very strong. The airplane is in restoration now but when I was flying it I used a 25 hour interval. It has a C-75/85, I have an oil filter kit that came with another Ercoupe but I will not install it because I read that they can cause the oil galley to lose suction while sitting and because as stated above; the engine will out live me.

  6. Jerry says

    I would definitely suggest getting a second opinion. I would strongly recommend adding an oil filter. And, continuing to change the oil at 25 hours and/or 4 months even with an oil filter.

    One second opinion I think you would find very helpful is Ed Kolin’s, the developer of CamGuard. He is probably the most knowledgeable expert on aviation oils in the world. He hosted a webinar in February describing what happens to the protective properties in aviation oil over the course of 25 to 50 hours of use. That webinar is available on his website at, under Tech Data and Presentations. It’s titled Aircraft Engine Life. Another would be Mike Busch, at Savvy Aviator. There’s a review from Mike on the CamGuard website.

  7. Greg W says

    Indeed the main reason to change oil is to remove the contaminants in the oil not particulates. Lead sludge will build (especially with synthetic oils) from the avgas,acids are created from combustion by-products and moisture from the heating /cooling of the engine. An aircraft engine has an “open” crankcase breather so even just the air temp. change from day to night will make an engine “breathe”. Is a filter a bad thing to install, no, is is truly necessary? I don’t think so. Most aircraft engines are damaged by corrosion, caused by moisture/ acids that a filter will not remove, that must be done by replacing the oil. The primary benefit of CamGuard is as a corrosion inhibitor, rust kills engines, abrasion/ wear from “dirty” oil does not. The best thing for an engine is to run it as often as possible, get the oil hot(to remove the moisture) and preserve it,(pickle it, CamGuard will do this short term) when it will be inactive more than a few weeks. Greg, A&P/IA

  8. Brett Hawkins says

    Jimmy, Paul is entitled to his opinion but I would ask for others. Recommendations on frequency of oil changes for most vehicles have evolved from the early days. When I was a kid Pennzoil recommended the oil in my Camaro be changed every 90 days, with, guess what?? more Pennzoil. Now semi-synthetic multi-vis automotive oils are good for 7,000 miles between changes unless you race in the sand dunes.

    Most of the contaminates in engine oil burn off if the engine is run for an hour or two. Further, when the engine sits most of the oil drips down into the oilpan.

    Paul, if someone left his aircraft unflown in the hanger for a year would it be wise to change the oil 3 times in a row prior to starting the engine (just kidding, sort of…)? And no, I don’t expect you to ask for a ride in my plan anytime soon.

    • Lee Ensminger says

      Brett, I *think* one of the major reasons behind the ability to extend oil change intervals in an automobile was the removal of lead from mogas. We still have TEL in 100LL. Also, a car engine has a sealed oil system. Airplanes still have the crankcase vent which allows moisture to be drawn into the engine-and the oil-thus making shorter oil change intervals desirable. Now, if you want to discuss why we’re still using 1940’s or 1950’s engine technology in piston airplanes today, that’s a completely different discussion. I’m a musician, not an engineer or mechanic, so these are just my opinions. Paul, any truth to what I’ve said, or am I wrong?

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