So it was time for my truck to have a good service so did the following and gained 40 miles on a tank of gas.260 miles on 14.5 gallons, now its gone to 290 for 14.5 gallons.My fuel gauge reads empty with 5 gallons left in the tank.
Oil and filter, nothing new there.
O2 sensor x2 (upstream sensors)both working fine just preventive maintenance, 150,000 miles on them.
Dropped the tranny pan, new filter,fulids
New spark plug leads.
Flushed the rad.
Washed the truck.