Does anyone tow with their s40 and if so what do you pull?
I've got a small, 20', sailboat and I'm wondering if the car can handle it
for light duty towing.

 

Check your owners manual for maximum trailer weight and hitch weight. What year S40?

For my 2000 S40, it lists 1100 Lb trailer w/o brakes, 2000 Lb with brakes and a 110 lb tongue weight...

I suspect a 20' sailboat to be over 1000 lbs so I'd say the answer is no unless you have a very light boat and a trailer with electric brakes...