Here's a bit more info comparing the M1 15-50 Silver Cap to the V-Twin.

Yesterday, we took out the 30 Cig Mystique, warmed over 575SCI's, @ 750 hp. fresh 15-50. These motors have run nothing but V-Twin since this run.

After about 7 miles at 5000-5400, oil temps rose to a bit over 260 deg. We have never seen oil temps over 220 on these motors, even hard running poker run hours. Oil pressure also was less than the V-Twin.

When you sit down and think about it, the V-Twin is double the cost of 15-50, but it still performs like new even after 15 hrs of hard running. (I change the V-Twin regardless at 15 hrs because of potential fuel dilution issues with blower motors) So in the end, yes the V-Twin is twice the cost but you get 50% more life out of it.

I'm sure the 15-50 is a fine oil for an automobile but for hard offshore running, I feel the V-Twin is a FAR superior lubricant.

Kurt