I've got a stock 2001 SLT, LB, 4WD with auto trans, 104K, owned since new and recently my everyday mileage dropped from 19 mpg to 16. 5 mpg. Then last weekend I was pulling a new 18ft enclosed V nose toy hauler (weight 3500 lbs) and my mileage was only 10. 5 mpg over 700 miles (no wind). This...