When I'm in the car I'm really particular about what "number" the volume of the stereo is on. It either has to be on an even number, or a multiple of 5. The "multiple of 5 rule" trumps the "even rule" though, so for example, it's preferable to have the stereo on 15 rather than 14 or 16 even though they are even numbers, lol.

Even if DH is driving and he changes the volume it will really bother me if it doesn't follow my "rules" until I change it. He just laughs at me now.