it sounds more like a Greg lyric) sort of supports traditional sexual morality.

With steam, heat, and rhythm in the back seat of the car

And adolescent perspective projecting life's forecast to the stars

You heard love from the lips and you were rapt by the hips

And the promise was eternal but you couldn't see that far

Maybe it’s more likely that the songwriter was attacking men who make promises they can’t keep, especially considering the other verse in the song. Either way, the choice of words (“the promise was eternal”) is definitely interesting.