Poor MPG's?

[PCA4208]

I have been getting pretty bad mpg's lately. Like in the realm of 10-11. I am planning on doing a spark plug change soon and was wondering if this would help things out? I've also heard that changing that upstream o2 sensor helps too. I'm at about 79700 miles now so I'm sure that these things would be worn by now. Any other things that could be done would be nice. Thanks

 

[jbrew717]

My '06 was getting 10.5 about a week ago and it ended up being a dragging caliper...

 

[KGBIGCOUNTRY]

Check your tire PSI also to see if they are low.

 

[PCA4208]

Tires are all at 32 which is the normal. Could it be anything else? I couldn't imagine that it could be.

 

[Hemi450hp]

If you have 79k miles on the stock plugs, then I would definately be replacing those ASAP. NGK 5306's and maybe a new set of plug wires since they are cheap. Clean/replace your air filter as well. I wouldnt mess with the o2 sensors unless you are throwing codes that point towards them.

 

[PCA4208]

Alright cool. I just figured the o2 sensor because they can sometimes read wrong, but I have no codes, so looks like just a new set of plugs and maybe even shorty wires.

 

[PCA4208]

Also just to be sure. The gap on the plugs is supposed to be .045 right?

 

[Hemi450hp]

I always gapped mine between .043 to .045

 

[LS5DodgeRam]

Did you upgrade your tires at all lately? I know I upgraded mine and got Falken Wildpeak A/T and I went with a huge size on a stock tire dimensions. the number comes out to be 32.5 inches diameter and 12.5 inches wide. I am still on the stock 28-29 inch diameter progam and that brought my mpgs from about 13-14 ish straight down to 9-10 real fast. I need a tuner to get the speedo and mpg meter corrected.
If you upgraded to a larger tire without programming it, the computer reads the rotations through a smaller diameter, which I believe you cover about the same distance with the lareger tire for the same amount of gas

 

[PCA4208]

Maybe that could be it. I have Falken Ziex TZ04's. It's a 305/50-20 tire so it brings it to about 31-32 inches. I also have 4.56 gears so that may complicate things. I might be getting a superchips 3865 here soon, so hopefully that will help things out.

 

[LS5DodgeRam]

If the tires are about 31 inches or so then that definitely it especially since you don't have the programmer, I'm trying to get the superchips flashpaq but its hard for me especially on a college student budget. I need to fix my calibration since my mpgs are being read incorrectly, and when my speedo says I'm going 65 I'm really going 72

 

[PCA4208]

I think my speedo is fine because I have many speed limit signs in my area. I'll put it in cruise at 30 and the sign will say like 31 or 32. But if it'll help. Also I'm on a tight budget too, being a high schooler without a job, it doesn't help having a guzzler lol.

 

[LS5DodgeRam]

yeah when I'm on my home street it does the same thing, the faster you go the larger the gap, if you have a gps like garmin or whatever... use that in your car while driving at city, residential, and highway and compare the speeds

 

[PCA4208]

I'll try that tomorrow, thanks.

 

[LS5DodgeRam]

Any time, glad to help!

 

[inktoxicated]

when i first got my 08 4.7 3.92ratio i was getting 13-14. i do mostly stop and go nearly no highways. its has 60k miles. i changed all 16 plugs out and the mpg didnt change at all. i used iridium denso. truck didnt run bad before i changed them but i just wanted to change them. well i had a shop do it. also changed pcv valve trans filters/fluids rear diff fluids. i since put on 35x2.5x20 and 6' lift which put on about 35-40 lbs on each corner. needless to say the power decreased and my mpg dropped to 10.5-12.0 dependant on how i drive. to get 12 i have to be the slowest veichle on the road. ive been turning the overdrive off a lot to on my around town voyages because it just gets up and goes better so with the increased rpms i know the gas is just burning away. its has a voltant cai and flowmasters too. when im going 75 the tach says 70

 

[PCA4208]

Changed my plugs today with NGK 5306. Took me like 3 hours in the cold. Original plugs were just nasty.

 

[sdamike]

Wow that is quite the difference, keep us posted if it helps.

Just a FYI, I just got a used superchips and am running the MPG tune, so far it appears to be helping a average of about 2 mpg...if I drive it right, trips where I would normally get a avg of 13 mpg, im almost at 15 mpg

 

[inktoxicated]

any power increase with the mpg tune

 

[Hemi450hp]

Mileage tunes on programmers are usually the worst tune you can run. You are better off running the 89 octane tune for both power and mileage. The 91-93 octane tunes are going to give the most power and mileage, but also come at the cost of higher fuel prices.