I've done some searching and can't find much. Is anyone using a 10W-50 for any Harley engines? For example, the Redline 10W-50's (Auto and Powersports) provide similar 100C viscosity, lower 40C viscosity, better VI, and similar NOACK as the 15W-50 and 20W-50 versions. The HTHS of Auto is 5.0 (lower than 15W-50 and 20W-50 by about 1 point). I asked about the Powersports HTHS and am waiting for a response but I'm guessing it's about 5.0 also. The HTHS of 5.0 seems like enough for an engine. The specs seem better for cool starts all the way to running temp, with the possible exception of HTHS, if 5.0 is too low. Any thoughts?