new spark plugs lower mpg??

[staindvans]

i changed a while ago and ever since then i have gotten a good amount less gas mileage than i was before i changed them. i don't think i did anything wrong, gapped them right, kept everything clean. don't know what the hell is wrong but i've gotten a max of 17.5 mpg that last 2 months and that was almost all highway driving. before i was almost certain i was getting more. anyone have a guess?

 

[DirtyKK]

i wish i could get 17.5 mpg's highway. what kind of plugs did you put in and at what gap?

 

[boebr1]

Might have knocked something loose? Maybe broke a wire? Maybe faulty plug (dropped on floor and broke inside then put back on shelf because it looked ok)?

 

[LibertyTC]

You may want to consider a complete tune up and possibly pull a few plugs, re-check the gaps, and see how they're burning. I tend to use the stock NGK's and change them every 20k miles.
Fresh oil (synthetic in winter) New air filter, a throttle body cleaning, IAC clean, and on those highway runs go one grade up in fuel and get a bottle Chevron Trechron added to that tank of fuel you will notice an improvement then.
Checking tire's Air pressure and consider like 3 lbs above your door sticker can help too.

 

[ThunderbirdJunkie]

Plugs aren't gapped properly or you used the wrong plugs for your application.

 

[staindvans]

i used motorcraft copper plugs gapped at .40. hows does one clean the throttle body and the iac? maybe ill try new plugs as well maybe i messed them up.

 

[kjweston]

I get 13 city if I drive it like a grandma without the A/C on.. wanna trade?

 

[Midgear]

I get 13 city if I drive it like a grandma without the A/C on.. wanna trade?

x2 :freak3:

 

[LibertyOrDeath]

x2 :freak3:

I got about 12 in my KJ, lifted.

I get about that in my XK, stock.

 

[ThunderbirdJunkie]

Don't mind ThunderbirdJunkie, enjoying his 16 city/21-22 highway.

 

[Marlon_JB2]

Why are you guys getting such crappy MPG?

I've never gotten anything that bad... with any Jeep.

 

[wheeee32]

Dang. I haven't did my mpg calculation in while but I've got 300 miles on my current tank with just under a quarter left.

 

[osufans]

after lifting, i only get about 320 miles/tank. EVIC reads about 18.1mpg, but that's probably a tad off...plus my fuel gauge plummets way too soon. i've tested it, and can go over 100 miles even after the fuel light comes on. most i ever put in was about 18.5 gallons, so i still had a gallon left (albeit that includes the lines, filter, etc...not all of that is in the tank.)

 

[LibertyOrDeath]

Why are you guys getting such crappy MPG?

I've never gotten anything that bad... with any Jeep.

I have a V8 and I live around a lot of hill. I also do mostly city driving.

 

[indieaz]

I recently switched josb and am doing all city driving. I feel like i'm driving "normal" and i'm averaging 18mpg. We normally get about 23-24 going 60-65mph, and 21-22 going 75mph.

 

[kjweston]

Why are you guys getting such crappy MPG?

I've never gotten anything that bad... with any Jeep.

I babied it real ******* the way to and from work today and got 14.7mpg but this is rare..


I have 265/75s and probably old plugs and dirty fuel system.

 

[Clyde Frog]

I'm averaging 16 lately, driving at a constant speed and not speeding. Technically 15.8 but whatevs. I have a little happy dance any time I see 18 MPG

 

[semper_rideo]

I get about 20 with 25/75% city/highway split. I don't baby it, but I don't race either.

 

[Dave]

With new plugs last year I got 20.5 or so almost all highway. Mixed is 18 or so and during the winter less, maybe 14-15 or 13 depending on how much it idles with the heater on.

Dave

 

[yellocoyote]

Winter fuel has hit our area within the last couple of weeks. I dropped from 15.5-18 down to around 16mpgs the last couple of fill-ups.