I do think that the boy’s maturity has a lot to do with it, but from my own experience, a lot of it is when are YOU as a father are ready to tell him.
My son is almost 17 and I told him a couple months ago. From a puberty standpoint, maybe I was a bit late, but he didn’t really start talking about sex, girls, etc until recently.
I always thought it was important though, especially before he became sexually active. I would rather be the one that told him “hey, you need some PE” than for his first time to be unpleasant because some girl was cruel.
Don’t let your son go out into the (sexual) world with inadequate equipment, especially when we know how to fix it
He’s now religiously doing PE, (DLD hooked him up with a good workout) and he and I are open about it. He’s part of the Brotherhood, and he’s very glad that I told him.
That’s the best part, is what it has done for the both of us.
So if you haven’t told your son about it, my opinion is it’s ok to let him know. You want to be the one that he can come to for ANYTHING and this really helps in all the relationship areas between you and your son.