Decrease in MPG

8246 Views 45 Replies 24 Participants Last post by The king of all ryans, Sep 17, 2008

378

Discussion Starter · Jan 7, 2007

I've been keeping a spread sheet of my fill ups and gas mileage. My fuel economy has been dropping and I want to know why. With summer over I'm not using the AC much and we don't have winter gas here in GA. I figured my mileage would go up as I got past the break in period. Any ideas? My driving patterns haven't changed. Here is a link to view an image of the spread sheet:
http://idisk.mac.com/bfregosi-Public
The file MPG.tiff is just an image file of the spreadsheet, the file XterraMPG.xls is the actual spread sheet (you need Excel to view). Take a look and post your thoughts.
ThanX

1 - 20 of 46 Posts

chiefkeith

· #2 · Jan 7, 2007

Are you the only one driving the Xterra? People have different driving styles from one another. Even yourself could drive differently on different days, and you may not even realize it.

Seems way too early, for your mileage to be so poor, to blame on any mechanical defect, but hey, I could be wrong.

Cymon

· #3 · Jan 7, 2007

Have you checked your tire pressure? I know that the Xterra has a tire pressure sensor, but that only comes on if the tires drop below a certain pressure. Even a drop in a couple psi for example 30-28 could reduce your mpg. I think to test to see if you consistently are getting less gas mileage you should take take out that variable and make sure that your tires are at the same psi every time you fill up. If they stay the same psi and you are still dropping in gas mileage then you know that it has to do with some other variable.

378

Discussion Starter · #4 · Jan 7, 2007

I try to keep my driving about the same. This is my daily drive now so back and forth to work at the same time same route. Usual side trips to grocery store, mall, gas station, the parental residence, etc., about the same. I will check the tire pressure and fill if I am low. Might be it, because I haven't checked pressure since the weather is generally cooler now. I'll get on it right now.

Edit- Just checked tire pressure: 34 PSI all around (Cold, haven't been out today) Must be something else. Any other ideas?

rusticle4

· #5 · Jan 7, 2007

I posted a comment about this very same thing, my first two months of owning the truck my mileage was about 17.8, now it is hovering in or around 12.1. I cant explain it, the dealership cant either. I noticed a drop around the same time I hit 3000 miles...but that is as close as I can get to an answer...

Lonesome Crow

· #6 · Jan 7, 2007

You might want to check you air filter, if it is excessively dirty it will impact your mileage. I have basically the same vehicle as you, 06 OR MT with 5300 miles on it. I generally get between 16 & 18 MPG, and I have a bad habit of messing around and speeding. I'm sure if I drove more slowly I would get better mileage. I do have after market exhaust but I have not shown much change form before.

378

Discussion Starter · #7 · Jan 7, 2007

I'll check air filter tomorrow. Still watching Giants/Eagles.

BoonDox

· #8 · Jan 7, 2007 (Edited)

I get around 16 to 20 on the hwy going 67mph,
i'm running 285/75/16. When i was running
my 34/10.5/17 ltb *bias* i was getting max 14
on the hwy sometimes 11 or 12. That was
through the computer mpg guage on the SE.
Also my guage digital display i read 61 mph,
64 on my speedo and 67 on gps WTF?
so is my speedo no correctly calibrated with the comp,
running on the 285/75/16,?
________
One Vaporizer

JasonK06X

· #9 · Jan 8, 2007

My gas mileage has gone to crap too. I don't understand it. I doubt winter fuel since I live down here on the Gulf Coast. I can't think of anything else it could be. Air filter is clean, tire pressure is good, driving habits the same as usual, etc....

Muzikman

· #10 · Jan 8, 2007

Last year i noticed an odd drop as well. One that I couldn't explain. Since then it's just gotten worse, but that is due to mods.

chiefkeith

· #11 · Jan 8, 2007

Also take into consideration any colder weather. Until the engine gets warmed up, it requires more fuel than normal to get the engine running and warmed up to get its best effieciency. Make sense?

Edit: Found this article on another website.. they explain it a little better than I did above.

Cold weather and frequent short trips can reduce fuel economy, since your engine doesn't operate efficiently until it is warmed up. In colder weather, it takes longer for your engine to warm, and on short trips, your vehicle operates a smaller percentage of time at the desired temperature. Note: Letting your car idle to warm-up doesn't help your fuel economy, it actually uses more fuel and creates more pollution.

Check this site out to track your fuel purchases and MPG:

https://www.fueleconomy.gov/mpg/MPG.do?action=garage

RiNkY

· #12 · Jan 8, 2007

Had to take my Yakima rack off 2 weeks ago after getting stuck in a low parking garage and not being able to get out without removing her. Since then I've been getting an extra 30 miles on a tank of gas, so she'll be remaining off until needed

hattrik21

· #13 · Jan 8, 2007

RiNkY said:
Had to take my Yakima rack off 2 weeks ago after getting stuck in a low parking garage and not being able to get out without removing her. Since then I've been getting an extra 30 miles on a tank of gas, so she'll be remaining off until needed

I can't say I've seen a decrease with my rack on but I drive all city back and forth to work and the fastest I get to drive is about 50 and that only lasts about 5 miles.

iandade01

· #14 · Jan 8, 2007

Has anyone thought that it could be more widespread use of ethanol? I read somewhere that it is really bad for gas mileage. Seems like a great way to lower emissions when you burn a lot more fuel.

rusticle4

· #15 · Jan 8, 2007

From day one I always ran 15% percent ethanol. I was using the same gas, from the same station, and got progressively less mileage. I put in a K&N, and it started to get marginally better...but then worse again. I am down to 12.8 MPG. Starting to get mad. I could have had a 3/4 ton Diesel, and got 17.

Muzikman

· #16 · Jan 8, 2007

Unless you are heavilly modded, 12.8 is way too low. I am sitting between 12 and 13 right now with 500lbs of armor, 33" tires, lifted and the aerodynamics of a brick on winter blend gas.

Blue_Orchid1

· #17 · Jan 8, 2007

Gas Mileage thing...

How does the ac compressor affect gas mileage? I mean, doesnt it come on if you have the fan setting on defrost and its not cold enough? When its not cold enough and i turn the fan on to defrost, i can feel power getting robbed.

My mileage haven't suffered too bad yet. I dont use the defroster though, unless the winshield needs defrosting. On the hway, i dont use the fan, i just leave the vents open and set a temp.

Hope this helps...

rusticle4

· #18 · Jan 8, 2007

yep nothing in the ways aero drag, or bigger tires. Stock height, stock tires, stock damn near everything. Dealer cant even guess what can be causing it. They adjusted my idle speed down 100RPM, but it didnt help. I am running premium gas for the next month or so to see if that helps. My sister got like 5 extra MPG going from ethanol to prem. I hope this helps, we will find out when my computer figures out I am actually feeding it something decent

rusticle4

· #19 · Jan 8, 2007

Oh and I took the basket off too, helped slightly...

Muzikman

· #20 · Jan 8, 2007

Re: Gas Mileage thing...

Blue_Orchid1 said:
How does the ac compressor affect gas mileage? I mean, doesnt it come on if you have the fan setting on defrost and its not cold enough? When its not cold enough and i turn the fan on to defrost, i can feel power getting robbed.

My mileage haven't suffered too bad yet. I dont use the defroster though, unless the winshield needs defrosting. On the hway, i dont use the fan, i just leave the vents open and set a temp.

Hope this helps...

Yeah the compressor runs with defrost and yes the compressor robs some power. I only use defrosters when I really need them.

1 - 20 of 46 Posts

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