Guys would you let your gay friend give you oral?

First that, second... How can I get my straight best friend to let me suck him off? I'm only asking because apparently it's common for straight guys to let their gay/bi friends suck them off. I don't need or care about any reciprocation, I just want to do it for him; to give him the best he's had and also cause I'd like it. Of course he knows I'm bi but the friendship is really important to me too.