Can I use an SAE 60 oil?

Dan Mooney, who has several round engine aircraft and a Skybolt with a Lycoming IO360A1B engine, has a question: Can he use oil from a drum of Phillips 25W-60 that he has for his round engines in his Skybolt? He concludes with, “”It gets pretty hot around Tulsa, Okla., in the summer.””


Dan Mooney, who has several round engine aircraft and a Skybolt with a Lycoming IO360A1B engine, has a question: Can he use oil from a drum of Phillips 25W-60 that he has for his round engines in his Skybolt? He concludes with, “”It gets pretty hot around Tulsa, Okla., in the summer.””

I checked with my good friend Paul McBride, who is the source for all information concerning Lycoming engines. He said that, as per Lycoming Service Instruction 1014, grade 120 or SAE 60 oils are approved in all Lycoming engines.

The interesting fact is that they are even recommended for operation above 80?F. I don’t know of anyone who routinely changes to a grade 120 oil in their Lycoming engine just because they will be flying in high temperatures. But changing to a 25W-60 should work well for Dan.

Teledyne Continental Motors also generally approves grade 120 or SAE 60 oils for use in most of its engines. However, the Phillips 25W-60 is the only SAE 60 oil that is approved.

The only difference between a 20W-50 and a 25W-60 or even a grade 100 vs. a grade 120 oil is the thickness or viscosity of the oil. To blend a thicker oil, all they do is change the ratio of base oils. The oils have the exact same components, just a slightly changed blend recipe. This means that the oils should work equally well in your engine.

However, there are possibilities for some changes with different oils. For example, thicker oil may leak less than thinner oil. This can reduce oil consumption. But, it is also possible for your oil consumption to go up with a higher grade of oil. This would usually indicate that much of your oil consumption is going past the piston rings.

The only precaution concerning using a grade 120 oil is cold temperature starting. If you use a single grade 120 oil in your Lycoming, I recommend that you change it out well before you get into freezing temperatures. This is not as much a concern with the Phillips multi-grade 25W-60, but I would still change to a lower viscosity grade oil in the winter time in Tulsa.

Ben Visser is an aviation fuels and lubricants expert who spent 33 years with Shell Oil. He has been a private pilot since 1985. You can contact him at Visser@GeneralAviationNews.com.

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