Ask the A&Ps

Join Mike, Paul, and Colleen for a second live session from EAA AirVenture in Oshkosh 2026 as they are try to answer the audience's most pressing maintenance questions.

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Join Mike, Paul, and Colleen as they take questions live from the audience at the AOPA tent at EAA AirVenture 2026.

Which oil is best, where is the oil going, running lean of peak with a carb, and how to fly a turbo are on tap for this episode.

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Full episode notes below:

Chris' American Champion Super Decathlon has an oil consumption issue. While his engine was apart after a prop strike the cylinders were honed, and he broke it in properly. He has since replaced cylinders, broke it again, and is still only getting three hours per quart. He said oil is coming out of the fuel servo, which everyone has told him is normal, but the hosts quickly disagree. Mike suggests borescoping the back side of the intake valves and looking to see if one is oily. If it is, chances are the intake valve isn't seating properly and is being sucked back up and burned.

Chris is trying to run lean of peak with a carbureted engine. He has an O-360 and he wants to make sure he's not doing anything wrong. His technique is to lean to the point of roughness and enrichen only enough to smooth things out. Mike said that's a solid technique and that most four-cylinder carbureted Lycomings run well lean of peak because they have a good balanced mixture distribution. Mike said not to worry about how lean he is. If the temperatures are within limits and the engine is running smoothly, you are good.

James has a Piper Turbo Lance and he wants to make sure he is running it properly. His manual has a five-minute limitation on takeoff power, and he's wondering where that comes from. Paul said the older Cessna 210s have a five-minute limit at 2,700 rpm, and they discovered that the limit was all about noise, and not about the health of the engine. They told James to check section 2 of his POH, limitations, which would require the procedure regardless of the reason.

Mason uses Aeroshell 100 plus Cam Guard. He's heard that straight weight oil remains on engine parts longer during periods of mis-use. But he read that Aviation Consumer tested oils and that corrosion protection was more correlated to added chemistry than viscosity. He's wondering if there's data to support either position. Mike said he'll recommend a multigrade for pilots who operate in a variety of temperatures. Mike things the cleanliness probably has more to do with Cam Guard use and operating lean of peak.

A fidgety fuel problem, octane ratings, and water in the oil are on tap for this episode. Email podcasts@aopa.org for a chance to be on the show.

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Full notes below:

Gareth has a turbo Arrow and he's been fighting a problem with fluctuation fuel flow. Sometimes the engine quits on the ground or runs rough in the air. They've checked the fuel spider, fixed intake leaks, overhauled the fuel pump, an exhaust leak, and much more. Paul is convinced that air is entering the system or there is a vapor issue. He suggests checking the heat shields near hot parts of the engine, etc. Mike suggests that it could be related to upper deck pressure, which controls the aneroid in the fuel pump.

Matt wonders if fuel octane impacts timing. He has a Cessna 150 and is running autogas, and he's wondering if his ignition timing should be changed to accommodate a difference in octane. Paul said the airplane was certified with 80 octane, so it's fine to keep the timing as it is.

Scott is wondering about an alternative to safety wire. A company called Bergen makes a safety wire alternative and he's wondering if it's legal to use on FAA certified airplanes. Mike said even if the company doesn't say it's FAA certified that it would almost certainly be a minor alteration, and therefore at the discretion of the installing mechanic. Paul uses them in certain applications and likes them.

Scott has a IO-540 on a Socata Trinidad and was about to overhaul his engine, but found Mike's maintenance philosophy. He's now at 2,300 hours and counting. Everything looks good except that water occasionally shows up in his oil analysis, and he's struck out finding help through his mechanic. The water is a byproduct of the combustion process. When you shut down the crankcase is full of steam, and that steam then condenses into water. You can help keep that water down by taking off the oil cap after shutting down, or by hooking up an engine dehumidifier. Scott flies about 100 hours a year evenly spread out, and he lives in a dry environment, so the hosts agree the dehumidifier probably isn't necessary.

Very cold cylinders, sort of warm cylinders, turbochargers, and pressurized mags are on tap for this episode. Email podcasts@aopa.org for a chance to get on the show.

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Full episode notes below:

Bill has a Cessna 182S with the Lycoming IO-540 and he has a temperature issue with his number 2 cylinder. Climbing out at full rich he would back up the mixture a bit at 1,000 or 2,000 feet and the CHT would climb to about 405. By going full rich again he can keep it below 400 degrees. Mike said the problem is totally in Bill's head. A CHT of 405 is a perfectly respectable temperature for a Lycoming. The redline on the cylinder is 500 degrees, so there's no need to worry about 405. Mike recommends keeping Lycoming cylinders below about 420 degrees.

Daniel has a Columbia 400 with a TSIO-550. He's been thinking about how car turbochargers don't have enough exhaust gas pressure to start working until a few thousand RPM and he's wondering if airplane turbos are the same. Paul said the waste gate closes immediately upon startup, so all the exhaust runs through the turbocharger from the beginning.

Bob is wondering about corrosion on pressurized magnetos. Mike has previously explained that they are prone to corrosion because of water entering the system. Bob wonders if because the water entering the system can only be in the form of water vapor and because the vapor is coming from clouds, which are low in the contaminate that cause corrosion, if Mike might be overstating the problem. Mike doesn't disagree with Bob's theory, but in practice the issue is real and prevalent.

Adam flies lean of peak in his Columbia and his CHTs can be as low as around 240 degrees and he's wondering if he's flying too cool and what he should do about it. Paul asks how far lean of peak he's flying. Adam thinks it's about 40 degrees, but at a fuel flow of 12.5 gallons per hour at an RPM of 2400. The hosts agree he's flying very lean. They recommend he try to fly about a gallon per hour more, which will get him a lot more speed and more normal temperatures.