This has probably been discussed a million times, but I read this on another site, posted by a petroleum engineer...very interesting. I know that the 06 CVO bikes are shipped with Synthetic oils, and I'm a firm believer in them myself, but had no idea there was so much variance. This is his post:
"Klotz is excellent oil altho a bit pricey, as you have found. Again, in synthetic engine oils, our (he's speaking of Ducati engines) engines simply do not need to churn a 50W oil. We are indeed robbing horsepower, the degree of which depends on the oil manufacturer.. Some 50 weights are just barely over teh 40W viscosity level yet meet the 50W requirements for viscosity allowable range. The thicker the base oil, the higher VI (visocsity index) (needed to achieve the side numbered designation (i.e. a 20W-50 or even 15W-50)) simply costs more money. Thus some oil companies produce a 20W-50 oil which *just* passes the 50W. Other, uncompromising oil companies produce a higher cost to manufacture 20W-50 that ends up in the middle or high end of the 50W range. Providing a much higher level of operational viscosity. So, even in 50 weights, all are not equal.
Same is true for 10W-40 engine oils. The top rated MCN (Motocycle Consumer News) oils (I am still searching for my articles!) held viscosity not only in testing but after running. These oils were in mid to high 40W at operational temperatures and provided the (theoretical) best film thickness at those times.
Best oils MCN recommended. Please keep in mind that I am biased (more by professional experience than by paycheck) but Mobil 1 MX4T 10W-40 (and the Mobil 1 motorcycle series) were among the 4-5 top rated oils.. The nice part of Mobil 1 MX4T (or Mobil 1 racing 4T or Mobil 1 V-Twin (20W-50) is that they are very reasonable cost-wise yet contain the highest cost base stocks, additive packages, etc..
There is some history with Mobil 1 motorcycle oils in that the former chief chemist owned 17 bikes and, nearing his retirement, asked Mobil to forget the gold watch and allow him to formulate ultimate motorycle oils. Mobil 1 MX4T/VTwin were developed and we have the good fortune end results of his work. All of this series are superb cost no object products resulting from his work and yet marketed at an excellent price.
And yes, I have seen it soooo many times on Dyno's I guess I could write a book... As example in all NASCAR racing engines. 99% are now running a 0W-30 Mobil 1... It is all about horsepower gain without sacrificing wear rates... We have a local motorcycle shop that "guarantees" a HP gain with Mobil 1 MX4T/V-Twin over mineral based oils. If a dyno does not reflect an increase the shop owner pays for the Mobil 1 MX4T and the dyno run. If an increase is shown, bike owner pays. The shop owner has never paid for a dyno run... Most of the dramatic gains are for those bikes that drove in with a mineral based 20W-50, change to the 10W-40 MX4T... And yes, the guy comes to mind that spent serious dollars on mods only to have the oil change achieve more; he was running a 60W! (as adivsed by the engine builder/modifier)
And yes, I would venture to say that your skilled right hand would be able to *easily* discern the difference in rear wheel horsepower for your engine with a 10W-40 vs. your current 50W. And yes, I have seen people spend huge sums of money for that extra 1 or 2 horsepower (NASCAR, again, comes to mind) when a simple viscosity change achieves the same end... Try churning a 50W with a hand egg-beater sometime then switch to a 40W.. You will be amazed at the difference..