I am not selling oil here, but I do have a recommendation.
I use 15-40 diesel oil in my bikes. Here's why:
It has the high-load package, that Detroit had removed from the SH - SM-rated oils, for fear of long long-term catalytic convertor damage. This is important for lubricating the transmission and air-cooled camshafts. It is Allison C4-rated, suitable for wet clutches, instead of having the friction modifiers Detroit insisted on to up the corporate gas mileage numbers. This is important to our XSs, since the poor exhaust ports and flywheels in the oil raise the oil temperatures. Many XS1s lost engines due to unnoticed slipping clutches that heated the oil and broke it down, causing engine failures.
Here are some examples.