Do the OBS trucks tend to get better fuel mileage than the superduty trucks, regardless of what season it is? I had a 97 F350 with intake and exhaust and I was getting 16 to 17 city and 20 to 21 highway not towing or hauling. I don't have that truck anymore. I have 99.5 F350 6wheel dump truck and only seems to get 10 to 12 city and 15-16 on the highway not towing or hauling. Seems like it uses more fuel than the OBS trucks. I don't know why same engine, same size tires, same tranny same gear ratio. It is bone stock with the acception of a DP tuner chip with 60 tow and 80 enconomy settings. I only noticed a 1 mpg gain in the econmy setting and I baby the throttle. I am not heavy on the foot at all. Does the split shot injectors make the truck have poor fuel economy, vers the single shots in the OBS trucks? Anyone got any answers for me?