Getting poor fuel mileage
Hello all I just recently bought a 2010 Freightliner Cascadia with a DD15 13 speed smart shift with 3.73 rear ends. At first I was getting 6 mpg which I was ok with but was hoping a little better. Now it gradually went down to about 4.5 mpg and seems to hover around that area. I've only had the truck for a week only did about 9 fuel ups. I generally pull 80,000 lbs thru the mountains. It's in the shop right now getting looked at to see why it's so low. I also wondering if the fuel filter is dirty how bad can that impact fuel mileage?
Is this a worthwhile discussion?