I have been seeing some very horrible MPG readings from my box, and I am wondering if I need to do something with the computer. You can check it out for yourself: http://www.fuelly.com/driver/ajcadoo/xb

I have a short ram intake, 4-1 headers and an exhaust, but i havent touched the car's computer. Is my car consuming more fuel than needed with the mods? Another thing I notice is significant slow down when I coast on the roads. All my wheels are fully inflated. It seems like my car maybe likes 3rd gear a lot because it feels like when i let go of the gas, it stays in 3rd gear and slows itself when i travel around 40 to 50. It just seems as though I am not getting very good MPG, and it is concerning me. The last tank I had 25 MPG with 80% highway at 65MPH. I dont get it!

 

TL;DR

you cant modify the ECU unless you go with an emanage of some sort. but staying NA that would not do anything but hurt you... Plus the ECU in the car is a learning ECU so its constantly changing... try changing your driving style, or read this... http://ecomodder.com/forum/EM-hyperm...ecodriving.php

 

Josh,
You have an automatic, is the shifter always locked in sport mode?? This will eat your mpg and hold it back form shifting at lower RPMs

 

There is no sport mode on the xB trans, but there is an overdrive on/off switch on the shifter... Is that what your talking about? If the OD is off then yes, the MPG would suffer.

the OD on/off switch is the smaller button on the shifter

 

Ok thanks for the info, no my O/D is not the problem. I only use that when I am accelerating onto freeways, but keep it on otherwise. Alright, then I will just deal with the MPGs. Its not a huge deal but I was just a little concerned. Thanks again.

 

25 really isn't that terrible... have you checked to see if you need to clean your airfilter?

 

Mine can hold its final gear going 36mph with very light throttle.
It usually coasts in 4th gear.

I'm sure you have reset your ECU after adding those mods.

 

You might want to put the "Sport Mode Handle" in the lower position, you know that long stick-type thing just behind the Gear Selector. That'll help a lot.

 

I think for the 20,000 miles that I tracked my MPG I averaged about 28.

Highway speeds kill our MPG. I was averaging about 245 miles to a tank this past weekend going to Atlanta and back. I have intake, header, exhaust, 15's and a Yakima LoadWarrior basket.

 

It's likely all in your right foot. You should be in 4th gear at 40-50 mph, not 3rd, so you're obviously hotfooting it. See http://www.fuelly.com/driver/frugalfloyd/xb for comparison. Mine is bone stock mechanically.

 

The comparison between our vehicles is eye-popping! We have the same # of fill-ups, but I have ~60% more miles driven, average 115 more miles/tank, have about 55% of the OP's cost/mile, and spent about 1/4 what he did this year on fuel. Plus, my last tank is darn near double his mpg. I've never seen a more graphic example of the cost of hot-rodding our 108 hp toys.

Sorry, ajcadoo. I'm not even sure an AT xB1 with headers and intake can beat a stock MT xB1 down the 1320 road.

 

When was the last time you gave the ol' girl a tune up?
Ya know new plugs , cleaned the air filter , and a good ol' oil change?

I have seen many cars go from great mpg to ____ poor mpg when they are in need of proper plugs ( gapped ), a new or cleaned air filter.

You mentioned that your tires were " properly" inflated , you running stock pressure in stock tires ? or stock pressure in after market tires?

 

Aftermarket wheels may be a problem. What size are you running?

 

in the two years of ownership i have never cleaned my air filter. that is something i should probably do....

 

hahahahaha, fo sho!!

 

Yup yup, but then again I dont consider myself a hypermiler.... I just want to save a few bucks at the pump, and my average MPG aint cutting it. But yeah, I completely agree with you!

 

In 2 years of ownership I have not replaced the plugs, no air filter, and an oil change every 4000 miles. Last oil change was i think 2000 ago.

I use standard Goodyear tires (the cheapest ones that fit on my box at Discount Tire). Inflated to specs in the doorjam.

 

The wheels are same size as stock, which is 15" I think? I dont know...

 

They may be heavier. Wider rubber will also give you more rolling resistance.

 

Time to replace plugs , clean the air filter or replace. And try putting 32 psi in those tires for a tank , I believe that the door jam says 29 psi w/stock size 185/60/15