2.5L ('98-'01) 10 miles per gallon?

[alt97million]

so i have a 1998 Mazda b2500 and every time i get gas i reset the trip meter and i have to fill up again at around 170ish miles. my math comes out to 10.5 miles per gallon. the downstream oxygen sensor was reading the same as the upstream. so i replaced the downstream and it was reading the same way, so i replaced the catalytic converter and the down stream reads normal. so its not a cat or o2 sensors. i have changed the dpfe sensor for the egr system and the connector for the dpfe sensor. the idle air control valve was stuck so i replaced that also. plugs, coils, and wires have been replaced about 5,000 miles ago. no visual fuel leaks and doesn't smell like gas after its been parked. idk why this truck drinks gas. I'm at a loss for what to do other than fuel injectors and I'm gonna get those checked out when i get the slave cylinder and clutch changed i plan on doing this soon just saving up for it. also i know the way i drive impacts fuel economy but i drive 10 miles to and from work and rarely get above 3k rpm that's usually when i shift gears. i think i drive alright im definitely not full throttle all the time i drive pretty leisurely .
has anybody had this bad of fuel milage or does anyone have any helpful advice? also the truck has 269,000 miles and i have no cel. i might can post some of the data from my scan tool if that helps.

 

[Brain75]

I would probably attack this more from a diagnostic than a throw parts at it and see if that fixes it (aka 'parts cannon')... grab yourself a v-linker v gate obd2 cable ($30-35) and a copy of forscan (free download)... and see what your live fuel trim is doing (while running), that will diagnose an injector issue and rule out some other issues.

if it is all factory default you should get 20 +/- nothing highway (all V6 rangers seem to be 20 +/- a pathetic amount) and at least 16 city.. the 4 bangers get great mileage compared... which would lead me to believe something major is going on with yours. Always in limp mode, or something worse.

if it isn't factory default (like lifted, 38" tires, carrying 500 pounds of winches/chains/6" thick bumper/etc) then we can start looking at 'excess weight'...

 

[alt97million]

this is what the fuel trim looks like. And it’s all factory stock tire size and stock ride height.

 

[Shran]

See if you can watch your coolant temp sensor readout while it’s running. Those failed fairly often on older trucks and had a dramatic impact on fuel mileage.

I went through everything on my ‘88 4 cylinder truck and it just never got better. I could get mid-high teens in the summer but it was 10-12mpg all winter long.

 

[ekrampitzjr]

See if you can watch your coolant temp sensor readout while it’s running. Those failed fairly often on older trucks and had a dramatic impact on fuel mileage.

Mine failed and my fuel mileage went down the tubes until I replaced it. Does your truck have a temperature gauge? Have you noticed it reading colder than usual? The gauges are damped to stay around halfway between C and H when warmed up. If it's indicating colder, then you need a new sensor and possibly a thermostat.

 

[alt97million]

the temps seems fine my scan tool is reading 190 degrees and my gauge is sitting right in the middle . another issue i don't have heat in the truck idk if that and the gas mileage issue has any correlation.

 

[don4331]

Take your truck for a 50+ mile hi-way drive each way. Check fuel economy after - I'll bet its not bad....

10 miles to work and back - the truck is still warming up and I'm including the warming of the oil in the transmission and rear axle in that. Noting any time sitting to warm up is 0 mpg.

 

[Curious Hound]

the temps seems fine my scan tool is reading 190 degrees and my gauge is sitting right in the middle . another issue i don't have heat in the truck idk if that and the gas mileage issue has any correlation.

Please note; the gauge on the dash gets its info from one sendor and the ECU gets its info from a different sensor. Your scan tool is telling you what the ECU sees. That is the important one.

 

[Brain75]

Take your truck for a 50+ mile hi-way drive each way. Check fuel economy after - I'll bet its not bad....

10 miles to work and back - the truck is still warming up and I'm including the warming of the oil in the transmission and rear axle in that. Noting any time sitting to warm up is 0 mpg.

Are the 4 bangers that bad? If we were talking about a V6 I would believe it was just a short cold trip issue, but I thought even cold the 4 bangers got better economy than 10.

 

[scotts90ranger]

I've heard conflicting things on 2.5L's... I think they got some odd tuning... I wouldn't expect it to be that bad...