# "That's an urban legend"

Page: https://stenobird.com/podcast/ask-the-a-ps-1305830/that-s-an-urban-legend
Text version: https://stenobird.com/podcast/ask-the-a-ps-1305830/that-s-an-urban-legend.md
Podcast: [Ask the A&Ps](https://stenobird.com/podcast/ask-the-a-ps-1305830)
Published: 2025-10-15T12:16:00+00:00
Episode link: https://traffic.megaphone.fm/AOPA7865438015.mp3?updated=1763406008
Audio file: https://traffic.megaphone.fm/AOPA7865438015.mp3?updated=1763406008
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JSON: https://stenobird.com/v1/public/podcasts/ask-the-a-ps-1305830/episodes/that-s-an-urban-legend
Duration seconds: 2985

## Resource

What's in our oil, how to keep cool (and warm), and lean of peak are on tap for this episode. Email podcasts@aopa.org for a chance to get on the show. Join the world's largest aviation community at aopa.org/join Full episode notes below: Mark flies a 182 and he read on a forum that the reason we've had so much spalling of lifters is because they took zinc out of the oil. Mike said this rumor has been going around for years, but doesn't make sense considering zinc was never in aviation oil. It's in STP, which is used as a thread lube. He cautioned not to put that in the engine because it's not ashless. The problem with lifters has been poor manufacturing, Paul said. Bob has an RV-10 and he's been trying to run lean of peak with wide open throttle. His technique has been to reduce rpm to get to 55 or 60% power and then lean. But doing so puts him at around 2,000 rpm. He's worried that running it too low might result in problems. Mike gives Bob a better technique. He said the mixture controls power while lean of peak, although running at a lower rpm is generally better since the combustion event takes longer. By running a lower rpm you're giving the engine more time to burn through the available fuel/air mixture. The low rpm prohibition that Bob is worried about in other airplanes is usually the result of propeller resonance issues, they say. Jeremy wants to know when to plug in the pre-heater. Other pilots have told him he needs to plug it in 10 to 12 hours before flying, but he's checked the temperatures with his engine monitor and found they rise about 35 degrees above ambient in two hours. Paul cautions that the oil won't be that warm, only the metal at the CHT probe, but because Jeremy is running multi-weight oil it doesn't matter. Mike said his rule of thumb is gene…

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## Transcript

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