Hey, guys. The rebirth of the 82 CB450SC is going well and I had a question. I came across a company who manufactures synthetic motor oil and I needed to find out if there are any 5W oil viscosities which will suit the Nighthawk? The manual says 10W40, but I'm not sure there were a lot of 5W oils around, that long ago. Does anyone have experience with other weight of oils in these bikes? Thank you very much.