mileage for a 4.3

well, i decided i couldnt wait to drive a truck while im rebuilding my other one anymore, so i bought a 95 k-1500 with a 5 speed, 4x4 and that 4.3 v-6 (i think it's the one that's the equivalent of a 350 that is missing two cylinders).

my main question here is what kind of mileage is the little 4.3, coupled with a 5 speed stick, capable of? the guy i bought it from says it should pull down around 20 on the highway in top gear if i keep it at 60 miles an hour. anyone here know the city mileage that is typical for these setups?

I usually get around 750km per tank combined city & highway on my 96 (2 wheel drive 5 spd 60% hwy/40% City). I would think you can easily get 20 mpg, more if it is all highway and you are not so heavy on your foot. I guess you can get around 550km per tank in the city.

Mark