Originally Posted By: BusyLittleShop
OP
In summary we all gave you our best learned opinions... key word in
your topic was and still is "TRACK BIKE" and true to its racing intent I
believe you want to safely extract the most HP from the 900RR...
typically owners spend a lot in aftermarket parts to improve
performance and thus improve their joy... leaving HP on the table is
not what a savoy track racer wants... a good after market exhaust can
cost $1800 to $2500 just to gain a precious 3 to 5 HP... a Power
Commander promises another another 6 HP... my experiences show that
running the recommended 30 weight oil prescribed in the owners manual
will also net 2 to 3 HP gain over a 40 weight and 4 to 6 HP gain over
a 50 weight and a 30 will still meet and exceed your track and mileage
expectations...
Oil drag in a tube comparison...
Not sure that an RC dropped in a column of oil and seeing which hits the bottom first is a form of racing, but it could be. That ball and tube effect is kinematic viscosity (what you refer to as gravity flow).
It was determined decades ago that with multigrades they didn't provide protection against wear as their KV (gravity flow) grades would suggest, and they started testing oils in very high shear rate regimes, which are typical of the loaded side of bearings, and the mid stroke of pistons and rings.
Found that the viscosity was markedly lower due to the Viscosity index improvers.
That's when they brought the minimum HTHS (high temperature high shear) requirement into J300.
Wear, power and economy are more directly related to HTHS than they are "gravity flow"...see recent discussions re some of the Unicorn 0W50s and the like, with ridiculously low HTHS, and meeting a "50" grade, based on "gravity flow" (rest of us call it Kinematic Viscosity".
First thing you've got to do to win anything is get to the finish line. That means adequate HTHS.
Second thing is to get there fastest.
And then you've got to balance the roadgoing racer that's not doing a rebuild every time out, or whether the risk/reward is in the check it over once, twice, thrice a season.
I'm positive that no motorcycle manufacturer has ever specified an ILSAC GF-4/5/6 (energy conserving) oil for a motorcycle application...they are low HTHS for unstressed economy applications.
the majority of the players in JAMA report gear pitting as ether a problem or present at lower then 3 HTHS.
So a "30" isn't a "30" in your simplistic view.
There are 30s which have decent HTHS (3.4-3.6) which will provide decent protection to combined engines and trannies...and they aren't ILSAC.