low mpg's and grinding noise from rear wheel's

[benzdude42]

I was given my 1984 300sd about 6 months ago and was getting about 27 mpg, but after about 3 months my mpg went down hill and im now geting 18.75. ive done everything i can think of; new injections, valve adjustment, new fuel lines, and new filters twice! so i jacked up the car to check for dragging brakes and the rear feel's way tighter than my 300d did. it sounds like a girding noise from both wheel's even with the rotor off. the calipers are fine and i've got new rotors on order. but even with the brakes off its still really tight. no wheel play that i can tell either. is it possible that the bearings are bad? would this cause my massive lost in mpg's?