I made 19 laps in the time. Chasing 5:00 laps I think is impossible.
Well designed game. The grass was suitably punishing compared to the track and the car handled mostly consistently. At times I felt I was hitting invisible walls, initially, until I learned the expected path. Trying to reverse into the pit was prevented for example, and I recall trying to follow the little yellow lines in the other way because they were acting as an invisible wall. But on my next playthrough I could drive right over them.
I never get round to requiring the player to refuel, maybe this was a last minute addition here? Anyway, you made it not feel like the chore that makes me not want to implement it.