Mike, Paul, and Colleen help an owner raise his oil temperatures, explain the rules around ELT battery replacements, debate the merits of a tuned exhaust, and help an owner whose airplane won't quit. Email podcasts@aopa.org for your chance to get on the show.

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Full notes below:

Chris has a Super Decathlon with CHTs as low as 270 degrees and oil temperature around 150. Even with the oil cooler covered during winter, it still doesn’t get hot enough. Mike said they like to see oil temperature up to 200 degrees if possible. Chris can check the vernitherm by putting it in boiling water to see when it actuates. Mike said the oil temperature gauge is typically reading at the coolest part of the process, and the oil may climb 40 degrees higher.

Curtis just wanted to change his ELT battery. His mechanic sent it away to a service center. He received an invoice with three options, none of which included replacing the battery. His standby current apparently tested high. Unfortunately Curtis was in an unusual situation with a foreign-produced part. There are two answers, Mike said. There’s the answer where you feel like you have to follow the manual, and one if you follow the regulations. The manual says the battery must be replaced by a Part 145 shop, but the regs allow the owner to do it under preventative maintenance. Mike contends that since the battery replacement section of the manual is not an airworthiness limitation, Curtis can just brush it off.

Pierre-Louis and his club in Switzerland have a tuned exhaust system on their airplane and while he is seeing some benefits in terms of fuel burn and climb rate, he is most interested in the smoothness of the engine. He said it feels like having a 6-cylinder engine and he’s wondering if tuned exhaust systems offer better engine longevity. Colleen thinks it’s possible the engine is actually working harder (more horsepower), so she guesses that the engine longevity would be reduced. Mike said he disagrees because the engine isn't producing more power, its power is being used more efficiently. Paul suggests that less vibration is ultimately better for the engine.

Frank has a Rockwell Commander 112 and when he shuts it down it sometimes diesels, or won’t entirely quit. Typically it only happens in the summer after a flight when it’s warm. Mike and Paul said the only way that happens is if the mixture doesn’t fully shut off the fuel supply. Mike said the mixture cable to the carb is the first place to check. Colleen suggests that it could be a leaking primer as well. Mike recommends fault isolating it by disconnecting the primer to see if it resolves.