interesting experience at the dealer's
The 4,000 mile oil change is approaching for my YZF600R, so I began looking around for oil to use. Went to the local Yamaha dealer and got a long lecture about the difference between motorcycle oil and automotive, expecially their different effects on wet clutch operation. According to the guy at the shop, automotive oil could cause the clutch to slip and its viscosity was severely degraded by the shearing effect of the transmission.
Well, I bought it hook, line, and sinker and bought four quarts of Yamalube 20W40 and a filter. Oops. I began to read up on the difference between automotive and motorcycle oil and found out there is not much difference. All contemporary automotive oil with an SG rating and is not energy conserving can be used and gives just as good or better performance than the motorcycle oil.
According to Motorcycle Consumer News, in a February 1994 report, Castrol GTX 10W40 outperformed Honda HP4 and Spectro 4 motorcycle oil. The Castrol degraded to 72.2% viscosity at 800 miles and then to 68% viscosity at 1500 miles, while the Honda HP4 degraded to 69.2% viscosity at 800 miles and then 65.6% viscosity at 1500 miles. The Spectro 4 degraded to 68% viscosity at 800 miles and then to 63.9% viscosity at 1500 miles.
Obviously, I should have read up on motorcycle oil before I went out and bought some. Live and learn.
I am not much impressed with 72.2% viscosity after 800 miles though. Maybe I should go with synthetic oil. The same test showed the Mobil 1 degrading to 86.6% viscosity at 800 miles and then to 83% viscosity at 1500. Maybe that's what I should use.