So i've had my 02 1500 for almost a year now and recently ive noticed my mpg dropped from a little over 13 mpg to 9 mgp. Oil is changed regularly and i recently did a Lucas fuel injector cleaner which brought the mgp back up to just over 11. My tire pressure is correct. I dont have a lift and tires only one size bigger than stock. Any ideas what could cause this and how to improve it anymore? Thanks in advance!