Did 4WD trucks get better mpgs in an earlier configuration?

Ihad a Ford F-150 6 cyl truck that was a 4WD and in those days you had to get out of the truck and lock in and lock out the front hubs to get in and out of four wheel drive. When locked out, the front wheel drive assembley did not turn. A few years later, truck manufacturers sold us the idea that we need shift on the fly and should not get in and out of the vehicle. This helped to create the SUV mania. My question is: were the older vehicles more gas efficient because they were not 4WD until you locked it in? Did they get the same mpg as a 2WD truck until locked in? Would a 08 Ford Ranger with lock in/out hubs get the same mileage as a 2WD until you locked in the front hubs?