I say his asking for the $15 is fine.
You say you often buy beers for people. He might be thinking of times when he has given you rides somewhere. It doesn't matter that you may think you are on the giving end most of the time, the bottom line is you guys are splitting up the costs of the road trip. The road trip cost $190. You put in $160, he put in $30. So $130 divided by 2 is $65.
The two things everybody here has in common; we all have above average driving abilities; and we all do more favours for our friends than we get returned.