Synthetic Oil Causes Leaks?
True synthetic oils (our government has decided that it's OK to label petroleom oil synthetic if it can be shown to perform as well as a synthetic!) often cause oil leaks. I have found this to be the case in older K gearboxes in particular. After having the pleasure of replacing the clutch in my K1 after the pushrod seal failed, I have not been tempted to try synthetics in my K1200RS.
Since I had to disassemble the gearbox to renew the seal in the K1, I had opportunity to check the rest of the box for wear. At 200,000 miles, mostly on petroleum oils, there was minimal wear.