What I thought I read was what I had read. Oil companies / blenders claim motor oil has little to no rust and corrosion protection without additives. Here are two examples from two different oil companies..
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I can't imagine all the others don't know this as well.
In my digging around last night I found articles related to piston aircraft as well and their oils that I found interesting. My friend Lance's dad owns two planes and confirmed what I read. Basically, air-cooled Piston aircraft engines use a straight mineral oil as it comes from the refinery in the weight required by the engine manufacturer, or mineral oil with AD (ashless dispersants) additives. The straight mineral is for break-in and the AD oil for flying, although some engines require AD for break-in and flying. Anyway, when a plane goes into storage over winter or even if its going to set idle for more than a couple weeks any time of the year, they have to drain the AD oil and put an aviation anti rust oil in because the AD will not protect from rust and corrosion. They run the engine up to temp to circulate the anti rust oil and store the plane with capped exhaust nand intake to minimize air and moisture getting into the engine.
All of this mineral oil rust protection really doesn't effect me anyway as I haven't used conventional oils in 4 cycles since the early 90's and as of close to two years now I think its been, I use synthetic 2 stroke oil. Not going to get into an internet pissing match over oil but I'll believe the oil companies statements on their own products.