Over on a motorcycle forum we are in a big long debate on using Shell Rotella T6 5W40 that is Jaso MA2 rated for wet clutch use. The main idea is that it is not what the Suzuki engineers qouted in the service manual. The manual lists 5W30, 10W40, 10W50 but not 5W40 and a (Anal Retentive) is saying we are stupid for using 5W40.

But my point of this is we have two British mechanical engineers members that have done testing of 'Car' oils in motorcycle engines that rev to 14,000 RPM. They say that car oils do not have the 'CLING' that true motorcycle oils do and at 14,000 RPM almost all oil is slung off cams and such.
It does not matter that 1,000's of motorcycle riders have used Jaso MA2 rated Delo 400 and Rotella T6 with no major failures. The Suzuki engineers are gods and they did not say it was OK. ??? 5W30 vs 5W40???