Some years ago we bought a secondhand 786B IH tractor with IH D310 motor that had done about 6000 hours, so i don't know what it was like new, but each and every day of use while we had it, it would not pull at its optimum until it had done exactly 20 minutes work, then it would pull like a steam train for the rest of the day. I have no idea why, it was just a very noticeable quirk it had.
Brett.
