There are figures of 2.8 million gallons/day based on the highest range estimate of 10% underinflated in the whole fleet likely on the road daily.
The real number is more apt to be around 600-700 thousand bbl/day of crude.
4.4 million bbl/day is ridiculous. If this number were to represent the high range of 10% then it would stand to reason that the other 90% was used as well for 39.6 million bbl/day which is twice the total used for all petroleum uses.
See my post #104