It looks like Ohio State has the lowest turnover differential (-4) among the remaining P5 undefeated teams.
Other good teams with similar TO margins have already lost at least once: Miss St (-4), ND (-3), ASU (-3), Mich (-2), Duke (-2).
Oklahoma is the only other P5 undefeated with a negative TO margin (-1) through the first five weeks.
Many of the other undefeated P5 teams have gaudy positive TO margins so far: MSU +9, Cal +8, (Houston is also +8 but not a P5), Utah +7, FSU +6, FLA +6, NW +4, Clemson +3, Baylor +3, Okla St +3, Iowa +3, TCU +2, Tex AM +2.
For a lot of teams on both sides of the ledger, fortunes will change (turnovers are partly random). It's my opinion, for example, that MSU just isn't as good this year and maybe they would have lost already if they didn't have a whopping +9 TO margin. Whereas I am confident that Meyer and company will effectively address the turnover bug and that margin will start to move in a better direction.