I ask this question as I plan on using 10W30 motor oil in my Jeep's manual transmission and need no sulphur added to the oil so that it is "yellow metal safe". I'm not looking to start a discussion around whether or not motor oil may be used in manual transmission but rather, looking for information on whether motor oil (synthetic or mineral) contains sulphur as an additive. I assume synthetic does not.
Synthetic based oils do not typically contain sulphanates. Mobil, as an example recommend Mobil 1 synthetic gear oil in lieu of a GL-5 lubricant that does contain sulphur and as you correctly state is injurious to copper, brass, and the like.