Look at oil field trailers, they have drive tires on them. Trailer tires have less rolling resistance. Drive tires usually have a more aggressive tread pattern and help in mud/snow.
For highway driving having an aggressive tread pattern like drive tires on the trailer would greatly increase the rolling resistance and increase your fuel consumption according.
Also many tires labeled as trailer only have about 14/32's while an all position probably has 18 or 20/32's.