I have been told that 14 mpgs is really good for a truck (my 1986 c20 does a bit better and its a v8 and carboratred). They are not little guys, and in this part of Canada you have more trucks on the road then just about any other type, most with one person in them and nothing in the back. At least I try to only use my truck when needing to haul yard waste or something to much for my little car, but next door has 3 trucks for 2 people.
7 to 8 Lt per 100km is about normal here (depending on what you drive) in non trucks but for years people here relate success with a big truck.