i have been running a performance castrol synthetic oil in my gas and my kdx has been faultless but i have just been made aware of problems with bikes that dont get used enough(i only ride 1 trail ride about every 3 weeks) .i have been told synthetics dont leave a residue like mineral oils in the bottom of bearings &in high humidity areas such as nz can rust the bottom of brgs this information was given to me by a motorcycle shop owner who also runs race teams.
I know the answer is to ride more but i would like other peoples experience to speak & or to teach people who park their bikes up too much
Do not use sythetic oils in your tranny. The extra lube can actually cause a lot of problems, the most obvious being clutch slippage. If you are going to use auto oil use standard types of oil, not synthetics.
Synthetics usually don't leave as much residue in the combusiton chamber. I've been into several Seadoo engines that ran synthetic premix and the lower end always had a nice oily film. These were ran at 40/1. I would keep running the Castrol and try to ride more.:D