NMK,
I'm a pretty new member and owner of a used '15 Z800. I wish I'd seen this before I change the oil in it last week for the first time.
Any chance we could start a sticky on confirmed alternative parts for the Z's? I posted a donut gasket that definitely works, the oil filters could be included along with your warning / info here so folks can proceed with caution. I recently saw on another board I joined, some parts store axles that fit also. I thought it might be useful. Sometimes using alternative parts is about getting better quality, sometimes saving a buck, and others it boils down to availability. Anyhow, thanks to your dedication to these machines. This forum has already been a wealth of info!