Oil

[flynrider]

Are we better off using the full syn 5w40 or conventional 15w40 Rotella..Which is more important the viscosity number or synthetic component Thanks for any imput..

Synthetic really has one basic advantage over dino oil. It has a much higher resistance to heat. To me that is important because I'm running an air cooled engine in temps that are regularly over 100 degrees.

I ran an oil analysis series on my CB750 when I was using dino oil. In the summer temps oil that started out as 20w-50 was actually a thin 20 weight after being cooked for 3K miles. Two options are to change the oil every 1500 miles in summer, or use a synthetic that won't degrade as much. I plan on doing an oil analysis series on the Rotella synthetic this summer to see how it holds up.

As far as viscosity goes, the first number in the multiweight spec doesn't matter much to me, as it never gets cold enough here for that to be applicable. The second number, the "hot" weight, is important. Honda's old recommendation for air cooled engines was 10w-40 in normal temps and 20w-50 for hot climates. I haven't run across a JASO-MA synthetic that goes to 50 weight, so I'm making do with 40.