2008 f350 squeal dropping mpgs

[bobmartin87]

i have a 2008 f350 dually and i was in the drive thru at dunkin donuts i notice oil light on and the mpgs on the dash dropping 6.0,5.9,5.8 and so on.i drive back to my work and check oil smells a little like diesel and looks a little overfull..i come out to take truck up town and get stuff for oil changes starts squealing and mpgs dropping...truck starts and idles fine motor a tiny bit louder and has a real loud squeal every miniute or so..truck has 124,000 miles on it...please help me thank you..