Poor gas mileage an power

Ok guy needs some in put my 91 b2600i is getting maybe 15 16 mpg an has less power than my 89 b2200. Have fresh tuneup any thoughts on y the mpg is so low an it's bout 90% in town

Timing maybe? Or possibly something gone bad in the ecu?

Mine is a 1991 2WD auto trans. truck and I get only about 16-17 mpg in town, but when it is on the highway where I can do 70 mph and get the trans in OD all the time, I get 25 mpg.

What truck do you have......2WD, 4WD, Auto, Stick, tire size?????

Funny, my 90 2200 is a stick, with stock everything, and it only gets about 20 mpg. It has a fresh set of plugs, cap, rotor, timing adjustment, etc. But like Earl said, when I can get and open highway run it gets a little better mkleage. I believe alot of my issue is my carb, I've just been too busy to tinker with it.

It's a stick with 4% smaller tires 2wd

I got a 93 ex cab b26 standard and I get about 23 exactly with ac and if I baby the throttle. Sometimes less. And I'm pushing 18s with straight pipe exhaust too.

I would say baby ur throttle and shift at 2k rpm every gear. Maybe change ur fuel filter and try use medium grade gas, n synthetic oil

I've been running 5-30 for oil, but on 87 or 89 octane I get close to 28 on the freeway, about 24 for regular driving. With my paper route and all the stop and go I've been doing I'm getting about 20/gal.

Wish I could get my mpg up I use top grade fuel an run royal purple. Gunna change the fuel filter again before I bout it the guy put a lil bitty chrome fuel filter been thinking the could be an issue.

I feel top grade fuel is a waste of time with low compression engines, they run better on lower octane. (humble and unworthy opinion)
But at least with a top grade octane you are (or should be) guaranteed octane... well if NZ and USA are anything alike