Can you use synthetic oil in a piston engine?

QUESTION: I am in the process of building a Zodiac 601 XL and intend on using an 0-235 Lycoming engine. My question: Can you use the Amsoil synthetic engine oil in this, or any other piston aircraft engine, without any problems?

Steve Dunn
Elwood, Ind.

ANSWER: Steve, congratulations on your Zodiac 601 project. It’s good to see you are asking questions before rather than after the fact. With regard to oils used in Lycoming engines, this entire subject is covered in Lycoming Service Instruction 1014M. While Amsoil is not specifically mentioned, as long as it meets or exceeds the specifications set forth in SI 1014M, its use would be OK. You must be certain it meets the Mil Spec. MIL-L-22851 or SAE Spec. SAE J1899 listed in the publication.

I believe Amsoil would fall under the category of an ashless dispersant type oil, so it should meet the specifications.

If you are unable to verify it meets these specifications, I wouldn’t take any chances. Instead, go with any good aviation grade oil that does meet the specifications.

I’ll wrap this up by making one of my favorite comments about engines: “”The two least expensive things you can put into your engine are gas and oil.””

Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to:

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