1991 B2600i fuel comsuption concern

Just recently bought a 91 b2600i 4x4 with low kms. It seems harder on fuel thatn it should be? Does anyone have any stats of what it should get, or any idea?

I have a '92 4x4 b2600i and recently replaced the O2 sensor and the fuel filter. I'm only on the second tank but it looks like my gas mileage is a lot better - 25%.
Though at its best I was only getting 16-20 mpg in town.

These trucks are just bad on fuel to begin with, I bought mine knowing that. But after-market upgrades will definately increase the mpg. I will be doing a whole new job on mine. Gunna do a killer exhaust, magna flow, with really wide diameter pipes, new header. Upgrade to K&N air filter kit. New o2 sensor. Tweak the internals with aftermarket cams and cranks and valves/springs.

I have a 92 2600i 4x4 and check my mpg carfully . This is my second one I had a 92 2wd bought new in 92 it did a little better in gas but not much.I average around town with the 4x4 16mpg driving it easy.These trucks are geared low I can take off in 2nd alot .On the hwy I can get 22mpg if I keep it at 60-65 .I have a fiberglass bed cover and a K&N (but I did not notice any measurable better mpg with the K&N) Some power improvment.I also have a big exhaust.The bed cover makes the most diff on the hwy.I you race around town and step into it you'll get 12-13.Whats amazing is I have a 1000lbs cab over camper and a 12ft trailer and the gas milage does not change much as long as I drive it easy I avg 15-16 hwy.