When you say say 2-3 hp up top, what is the baseline hp of the engine in question and what is the hp of the same engine running the lighter oil?
I can feel the difference on the seat of my pants but some riders can't... however the dyno proves a rider enjoys a HP boost between a 30 and 40 with no loss of longevity... try it and see if you can tell a difference... you have nothing to loose except unwanted parasite drag...
Quote Sportrider magazine...
"Some oil manufacturers and their representatives claim that using
their product will result in more horsepower. We decided to put these
claims to the test-an actual dynamometer test. Two of the full synthetic oils in
this test make these horsepower claims on their labels: Maxima Maxum
Ultra (in 0W-30 and 5W-30) and Motul Factory Line 300V (in 5W-30). We
took two open-class sportbikes-a Suzuki GSX-R1000 and a Yamaha
YZF-R1-and ran them with common off-the-shelf Valvoline 10W-40
automobile mineral oil to set a baseline dyno run. That oil was
drained and replaced with the 0W-30 Maxum Ultra in the Suzuki, and the
5W-30 Motul 300V in the Yamaha. After about 15 miles of running to get
the oil fully circulated through the engine, the bikes were then
dynoed again."
"Lo and behold, both the Suzuki and Yamaha posted horsepower gains.
While not an earth-shattering boost in power, the gains were far
beyond common run variations, and weren't restricted to the very top
end. The GSX-R1000 posted an increase of 3.3 horsepower on top, with
some noticeable midrange gains as well; even more interesting was that
the power steadily increased for several dyno runs (as the coolant
temp increased). The Yamaha responded nearly as well, with a 2.7
horsepower boost on top. It should also be noted that while riding
both bikes, there was a noticeable ease in shifting with the synthetic
oils compared to the automobile mineral oil. Pretty impressive for
just changing oil, in our opinion."