[Zeke]

Originally Posted by speeder

OK, thanks. Why straight mineral oil for aircraft engines?

I thought he explained,

Originally Posted by Tim Hancock

I was taught to always run mineral oil in aircraft engines for break-in. It allows the rings and cylinder walls to make metal to metal contact at any high spots. If regular oil was used during this time, the cross hatching could glaze over thus preventing the ring seating process. After the first 50 hours of running engine hard, we switched to ashless dispersant oil for normal continued operation.

Here is a link that explains the reasoning as it relates to aircraft engines.

https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart08-30071255.html


Some of the oils I kept in stock when I ran a side business working on aircraft.