Being 16 years old, he's most likely interpreting "love" as the relationship type, not the parent to child bond. He's saying "love you" as a trained response because you have taught him this. I'd ask him to tell you, any way he can, what his view of love is. Depending on his answers, you can go from there. There are many kinds of love as we all know, but he might not understand this. It's your job to help him figure this out, no matter the ASD or any other thing, like being a human being. Tony Atwood's books are great at helping with this.

If it helps, my 12 yo always says, "I guess I love you, but I'm not really sure I know what that means." It may be a concept your son can't put into words to understand, even if he does feel it for you! :)

other days I simply said thats ok maybe u will love me tomorrow, but i still love you.

I get the "love you" back sometimes and and occasional half a hug, but my 13 yo son on several occasions that he only cares a tiny bit for me and doesn't love me. When I ask him who he loves he says his dad, all siblings,except one, various other family members and the dogs. I really believe that it's because I'm the rule maker and I make him do his homework, and I make him put down the video games etc...to do things he doesn't want to do.

I used to tell my son who just turned 16 yesterday..... "that's ok, but I still love you." My son used to not express feelings at all. He would say he loved no one and he didnt get hurt because he had no feelings.