He Said, She Says

For some reason I tend to fall into a natural writing rhythm that is in the present tense. For example, I'll be writing along and without thinking the following paragraph comes out:

"Ahead I notice Carver changing lanes. Moves to the left, then left again, then back right. Ordinarily I might think he was trying to pull something — maybe he knows something's up — but during three days of following the guy I've learned he's just an erratic driver."

Then later I realize I've switched tenses and have to go back and clean it up. If present tense feels more natural to me, then maybe I should just go ahead and write in it? Problem is that whenever I read a book in present tense it feels like an affectation to me. It may be more acceptable now than it used to be.