I don't believe the brand of oil is all that important, as long as you change it frequently enough. I use Purolator Pure One filters, which are very highly rated. I use Valveline or Castrol 10-40 motorcycle oil, but I recently bought some Shell Rotella T6 Synthetic 5W-40. It's JASO MA certified, approved for motorcycle wet clutch use. I change the oil at 3-4000 mile interval, or whenever it starts looking dirty. Really, oil is oil. I used to hear "bad" things about Castrol GTX, like it builds sludge in the oil pan. I used Castrol GTX 20W-50 exclusively in my 1986.5 Nissan pickup w/3.0 liter V6. I changed oil every 5k miles for the first 100,000 miles, then every 3K miles for the next 100,000 miles, then every 2,500 miles for the next 75,000 miles. Then I finally sold it after 20 yrs and 3 months, and 275,000 miles. The one and only time the engine was opened up was at about 200,000 miles when a cam had to be replaced.
The Consumer Reports oil test on NYC taxi cabs proved that. Their findings were "every brand of oil performed as well as the next, with every engine showing no significant signs of wear" after being torn down and all tolerances measured.
AKA The Green Hornet