Is it okay for a 18 year old guy to date a 20-25 year old girl?

Sure...but why would a 25 year old girl want to date an 18 year old guy?

You are both adults in every state in America, if she likes it, who cares who doesn't?

Of course, why not.

Not 18 and 20, is different from 18 and 25.

But no problem with any of them, if they girl does not care.

Of course my wife is about 15 years younger than me. But in college I dated a girl two years older, never a problem.

You can, but you aren't going to find a lot who will... 18 is really immature to someone in their 20's. (Seriously, you will notice this in others yourself in just a few more years) You share more with high school kids than you do the over 20 crowd. I dated women a few years older than me but I was over 20 at the time.

Of course there is a big enough maturity gap....between 18 and 25 I'd question as to WHY she would and what she saw in someone still wet behind the ears (figuratively speaking) .....but a 20 year old will have a much smaller maturity gap. Yes people DO go through that much maturing during those years (up to the late 20's after which it slows down considerably)

You were just crushing on some 17 year old. You get around a lot.
I can't imagine why a 25 year old woman would like an 18 year old.
20-25 is not a girl, she is a woman.