MPG any thoughts?

[gardengirl38]

I have a 2006 Unlimited Stock.... I am getting 12mpg city. This is just horrid. Is it just the way it will be or is there anything I can check to see if something is wrong???

 

[54cj3b]

sounds about right if its city driving

 

[jfrabat]

12 is a bit low IMHO (not unheard of for a Jeep, but low considering yours is pretty much stock); I get ALMOST 15 with 33's and 4.88 gearing...

 

[Dittrich31]

the only little things that I would do is check your air filter, possibly put in a kandn, put in some fuel injector cleaner, maybe time for a tune up. Proper maintenance and a steady gas peddle can go a long way.

 

[JPNinPA]

I have a 2006 Unlimited Stock.... I am getting 12mpg city. This is just horrid. Is it just the way it will be or is there anything I can check to see if something is wrong???

If it is lots of stop and go and your heavy footed with bigger tires this could be right. But for normal daily commute this is low. What it your highway MPG? Any Idea?? Is your check engin light on?
I have an 05 unlimited with a 2.5 in lift and 33X 9.5 tires manual trans and get 16-17.5 around town and 19-20.5 hwy. I do have additional mods intake and exhaust...
Things I'd check first would be plugs, air filter, tire air pressure, run some injector cleaner. Also it could be the gas you are using. NOT octain but % Ethanol. These 4.0 engines do not do well on high % ethanol. I check my MPG often and when I moved did at least eight 500 mi trips. I noted where I bought gas. Stations that noted they did not have ehtanol added, actually gave better MPG. Some others did well also.

 

[gardengirl38]

Thanks for your comments.... here is what I know lol.
I have a new K&N air filter, new plugs, tire pressure is good. yes i guess i have a lot of stop and go but I am not heavy footed I dont think... I will get some injector cleaner.

I am not sure if I have any choices to fuel without ethanol added... everything seems to be 10% ethanol everywhere I go. Could be a Virginia thing or ? If there was a place that didnt have that added I would definitely use that. I have really bad spark knock or what I call spark knock anyway... even if I use higher octane gas. Doesnt seem to make any difference there. I buy good gas as far as brands of stations. Highway I get between 16 and 18 mpg. If its not uphill driving its at the higher end of that but I do a lot of driving in the mountains the trip up is bad but coming home is great haha. I am just wishing that there was some way to improve it a little bit its costing me a fortune to keep fuel in it.

 

[JPNinPA]

Okay. Is this an auto or manual trans? Tell more about the knock. When does it happen and when doesn't it. WHen did you note teh bad MPG before or after the spark plugs? From what you tlod so far there could be two or more things. One being the plugs were not installed correctly possibly withthe wrong gapping. Knocking will be detected by the knock sensor and will retard timming and result in lower MPG. Knocking also could be lugging if you have a manual trans and do not give it enough gas when pulling out. Consistanly doing this is like knock and result in the same. Plus it is not good for the engine.

Between 16 and 18 highway is about correct for stock.

 

[54cj3b]

ethanol alone kills gas milage

 

[TerryMason]

Try tracking your milage for a while at fuelly.com. I'm a big fan of that site - it gives you a better idea of your milage over time



also, what size tires do you have? Larger tires will throw your speedo off, and make you appear to get fewer miles per gallon.

 

[jayh]

keep in mind that the 'city driving' figure is NOT stop and crawl city driving. It would be described as more of a suburban driving periodic stopping and going.

 

[Saddle Tramp]

12 MPG sound low to me, 16 – 17 mpg is more like it in a TJ but you have an unlimited which will be heavier. Also a lot of the unlimiteds I have seen even though they are not 4 cylinders or Rubicons have 4.10 gears in the pumpkins, if so that wont help the mpgs.

 

[xt master]

2.5l,31" tires,4.11 gears,heavy foot...14mpg city 17mpg hwy.

I try and keep my RPM's some where between 2000 and 3500..Best power for my Jeep.

I have also started to use the online fuel tracker like Terry.My Jeep is not an every day driver so I only get fuel every other week.So far only 2 fuel ups since I started to use it.

 

[JPNinPA]

also, what size tires do you have? Larger tires will throw your speedo off, and make you appear to get fewer miles per gallon.

It says Stock in her details.

12 MPG sound low to me, 16 – 17 mpg is more like it in a TJ but you have an unlimited which will be heavier. Also a lot of the unlimiteds I have seen even though they are not 4 cylinders or Rubicons have 4.10 gears in the pumpkins, if so that wont help the mpgs.

Unlimiteds have 3.73 gears stock and weigh is 3721 lbs vs 3,200 lbs. - SE, 3,438 lbs. - X, 3,539 lbs. - Sport, 3,832 lbs. - Rubicon So they are not that much heavier.

 

[Team Twisted Off Road]

1997 TJ 4.11 gears 2.5 31" tires 5 speed i get 12-15 with my foot in it........redline fever:MDB2:

 

[gardengirl38]

Thanks again for all the replies. Its an automatic trans. I noticed the bad fuel economy just in the last few months but before that I cant say I was really paying attention. It just seems like now I can litterally see the gauge move uggh.
As for the spark knock- i think it was happening before the new plugs, thats probably why we put those in but again my memory fails me. I will go out there today and check the plugs for the proper gap and also look at the condition of the plugs... I will check the air pressure in the tires as well, seems like that is always low no matter how often I check and I know that affects mileage. The knocking happens pretty much whenever I give it gas. It is worse when going up hill. It isnt noticable when I am going slower like up to 30 but after that I hear it... Its not horrible knocking like I have had in some really old crappy cars but I can hear it so i know its happening and I know its bad for the engine so it bothers me. I have used higher octane fuel and it does not help it or at least not to a degree where I can really tell the difference.

 

[gardengirl38]

Ok have one more question for you.... in checking my plugs I decided that I will buy what the hood info recommends for the vehicle instead of what I have in there.... I couldnt remember exactly when it was done. They didnt look too bad, looked like the little electrode was gone from two of them as well... I am cleaning my K&N and that doesnt look too bad either. Here is my question- I noticed that I have some oil coming out of my Valve cover breather..... its wet with oil around the flat plastic plug that touches the valve cover does that make sense? Then about a 6 inch all around that area has oil on it.... no other leaks of any kind.

 

[JPNinPA]

Okay. The 16 to 18 mpg hwy is recent? And are you throwing any codes? I ask because when I was having issues there were codes and mpg were bad all the way around. Hope to hear what you find after checking the plugs. Did all the plugs look the same or was any one or two much cleaner? Check for codes too.

 

[gardengirl38]

There were two maybe three that looked better than the rest. Not extremely different but you could definitely tell a difference. Yes I got better mileage last summer for sure seems like its noticable worse now. I will check for codes. Thanks!!

 

[JPNinPA]

Ok have one more question for you.... in checking my plugs I decided that I will buy what the hood info recommends for the vehicle instead of what I have in there.... I couldnt remember exactly when it was done. They didnt look too bad, looked like the little electrode was gone from two of them as well... I am cleaning my K&N and that doesnt look too bad either. Here is my question- I noticed that I have some oil coming out of my Valve cover breather..... its wet with oil around the flat plastic plug that touches the valve cover does that make sense? Then about a 6 inch all around that area has oil on it.... no other leaks of any kind.

Missing or worn center electrodes will do it. It's like gapping them too wide. Spark will not be enough or happen at the wrong time. Just be sure to check the gapping . Just because they are new doesn't guarantee they are correct.

Also a little oil around the breather is normal. You could pull the IAT Intake air temp sensor and make sure it is clean and look check how clean the throttle body looks. Again a little around the breather is normal.

Check out this link about plugs that may help you out if this continues and you want to know what may be happening.

http://www.gnttype.org/techarea/engine/plugs.html

 

[JohnnyO]

Different parts of the country get different kinds of gas at different times of the year. If you get the crappy oxygenated gas in the winter where you live, that will cause knock and hurt gas mileage. I would put new plugs in to make sure, but also disconnect the battery for about 15 minutes to reset the computer (this works on the Fords that I'm more familiar with, I assume it would work on a 2006 Jeep), and see if 89 octane gas makes the knock go away and helps the mpg.

Also when you're sitting at red lights you are getting 0 mpg.