Ive wondered that myself. The scion I owned and honda required 0w20 but this car takes regular old 5w20. The other cars had yearly ten thousand mile oil changes, the V its back to every 3 thousand miles.
Ive put 5w20 in my other cars when I couldnt find 0w20 and I didnt notice any mpg difference, but it was still a pure synthetic oil.
I just assumed the varable valve tech in the V is like that of BMW which requires frequent oil changes as crap in the oil can screw it up. Ive read the nissan valve tech is a knock off of the varable lift, but any more info is hard to find other than it uses plastic parts.
On hondas the vtec is oil psi depended and dirty oil will clog up the vtec filter and cause an error or low oil psi light when you exceed the rpm to trigger vtec.