The International Cessna 170 Association

I apologize in advance if this subject has been beat to death but my searches don’t seem to turn up specific answers.

I’m looking at purchasing a 1955 170B with 800 hrs on the engine. Since at least 2006 from his records, the owner has been using 80W Aeroshell. I’m thinking “Geez...80 weight?” That’s almost like the 90W I use in my SUV differential.

Anyone use this? Seem abnormal?

Thanks
Phil

Aviation oil is not often referred by it's weight. 65 is 30 weight, 80 is 40 weight, 100 is 50 weight, and 120 is 60 weight. Multi viscosity oils are referred to by their weight and then the weight they act like. 15w-50 is a 15 weight oil that acts/protects like 50 weight.

80 is an appropriate oil in most places in the US for most of the year. When it gets over about 80F you probably want to switch to 100. If your operating in cold climates you might want to use 65. Problem is much more than 80 and 100 are not readily available and may only be available in mineral oil.

Multi viscosity oils in aviation started to appear or have become more popular in the '80s a decade or so behind auto oils, as the chemistry was improved and proven.

I use multi viscosity oil cause I don't fly enough to change the oil but once a year and the temps I might fly in range from 25F to 100F.

Oils, like many things are personal it seems. I prefer for example to us Philipps 20w-50 cause the 20w is just a tad heavier than Shell 15w- 50 though both of these oils protect like they are 50 weight. BTW I've also run 80w and 100w in my Continental A-65, C-85, C-145 and Lycoming 0-320.

Thanks Bruce! So it doesn’t mean the thick oil is holding the engine together...? Good news.

Phil

BoisePhil wrote:Thanks Bruce! So it doesn’t mean the thick oil is holding the engine together...? Good news.

Phil

It means this engine has, so far, been proven to be held together with 40 weight oil which is thinner that 80w.

Although not related to aviation, an interesting and informative website for oil info is: https://www.bobistheoilguy.com/

It's also interesting that gear oil SAE standard weights also do not conform to engine oil standards. 80/90 gear oil is considerably "thinner" than the numbers might indicate.