Our 06 250 SD has a 5.4L with a K&N air induction kit and a super chip and it seems to get 10-12 no matter what its doing, even empty. Our enclosed trailer is 24ft long and always loaded with equipment totaling (with trailer) about 8k. Our 05 F350 SRW has a 6.0L PowerStroke and we just got it so I can only guess from what Ive read and heard expect to get mid teens. I think for around town towing and occasional hi way towing your better off with a V-10, Ford's V-10's put out almost 500lbs of torque!
J and B Lawncare:
On our own as of 2003. Proud to be a full time, legitimate company.
Equipment we use:
Pro Line and GatorMade trailer's
Gravely, Exmark, Honda and Snapper mower's
Echo trimmer's and blower's
New Holland and Dresser loader's (snow removal)
Fisher snow plow's
DownEaster and Fisher salt spreader's
TurboTurf fertilizer tank