Convinced: Oil Viscosity & Performance.

[AdrianR]

Bottom line for the utmost performance use what Honda recommends!  10W/30 oil! (for moderate climates)  I just changed the oil last week. I had been running both Honda and Amsoil 10w/30 full synthetic oil.  I switched over from Valvoline's 10w/40 conventional motorcycle oil at around 1800 miles.   That was actually very good oil...especially for conventional oil..  However, when I switched over to full synthetic 30w oil and noticed not only the obvious quieter run, smoother shifting etc...(what synth oil provides)but *slightly* more HP...  The bike just revved faster...

When I changed the oil last week I thought I would try 10w/40 full synthetic oil (Castrol racing 4T). I was curious how she would run. The bike of course ran fine, but man that *snap* was gone...especially at a proper running temp when she develops maximum HP.

This morning I went to O'Reilly auto parts and bought 4 qts of Lucas Oil full synthetic 10w/30 metric bike racing oil.  After a short 10-15 minute run that *snap* was back!

Convinced.  Run 10w/30 for max performance.

(incidentally I also experienced this with my Ford truck.  Ford recommended 5w/20 oil..but I thought it was too light and ran 5w/30 for several years. Accidentally I had purchased 5w/20 and only noticed it after I drained all the oil out of my truck's Triton motor.  I obviously filled the engine with that oil and WOW...more HP!)

(Since the Castol oil only had about 200 miles on it I kept it. It will be used for topping off all my engines between oil changes.  This stuff is too expensive to waste!)