So I've got a problem :(. My 1998 Ranger has been declining in its fuel economy for the last year. It's got the 2.5l and the 8.8 inch rear axel 2wd. I've been able to slow it a little with replacing wheel bearings, replacing tires, etc. But it is still declining and its getting to the point where it is a little more expensive to drive than it should be. People I've talked to have said they get over 19 miles a gallon on their Rangers but I'm somehow getting 16.3mpg on average. Now i was getting just over 18mpg years and years ago, I mean it was a pretty fuel efficient little truck, but now, not so much. I had my mechanic replace the exhaust system 1 year ago because the cat had collapsed. Is it possible... they replaced everything except the o2 sensor? if they didn't then it is a 15 year old sensor, if not...

I guess what I'm trying to ask is how did i got from over 18mpg to 16.3? I'd like to see the trip meter read over 300 miles on the tank when i go to fill up again.

Thanks,
James P

 

O2 sensors are responsible for MPG...................so not sure why they were not replaced
O2s are actually the ONLY sensors that wear out, 12 year or 100k miles and MPG will start to decline

1998 has two O2 sensors replace both
I assume you have changed the spark plugs at some point

My 1994 Ranger has all original sensors except for new O2s every 10 years or so, at 450k

 

Winter blend vs summer blend gasoline can effect mileage if your state uses them

Higher ethanol levels can also effect mileage

 

Yeah, replaced the sparkplugs when the timing belt snapped.

Thanks, RonD!

That Fuel economy I stated is correct for the 8.8in rear axel?

Edit: I don't know if TN uses the different blends or not, but i don't seem to have much of a fuel difference in either season other than the slow continuous mileage drop. I also use 87 in my truck.

 

Axle size and ratio don't matter that much, as long as engine is staying in good RPM band for speed
Tire diameter matters in that the Odometer/speedometer was setup for Stock tire diameter

I.e. if truck came with 27" diameter tires and it has 28" now then odo/speedo will be off, and off LOW, so 100miles travelled would only show 95 on odometer, 5% low
You can get GPS on your phone and on a straight section of road see if speedometer matches up, i.e. if GPS says 65mph and speedo shows 61mpg then its OFF and off LOW and odometer as well

So after a tank full and only 275 miles you may have actually gone 300 miles

 

Didn't know that and now I do! Okay tires are right size, I lined them up with what the vin said.
If none of the Axle ratios matter, then replacing the Oxygen sensors should put me in good shape.

 

Yes, but check speedo/odo as well just to be sure

 

So I'm actually running about 2 mph high on the odometer.

 

At what speed? and which way, reading faster or slower than actual speed?

2 mph off at 100 mph is only 2% - not going to make much difference

2 mph off at 50 mph is 4% - going to make a little difference

2 mph off at 25 mph is 8% - will make a big difference

 

Going about 60 mph odometer reads 62 mph while gps reads 60 on interstate based on what I saw last week