FAQ - My gas mileage sucks - Page 2 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > General Technical Discussions > Engines & Drivetrain > FAQ - My gas mileage sucks

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineSpartan Locker Promo Running now @ ROCKRIDGE 4WD plus FREESpartan Locker Special Forum Prices Dana 30 44 60 Ford 8.8

Reply
Unread 08-28-2010, 04:13 PM   #16
Willy36
Registered User
1990 XJ Cherokee 
 
Join Date: Dec 2007
Location: FoCo, Colorado
Posts: 1,168
Quote:
Originally Posted by LuckRider View Post
I read that any vehicle built after '93 uses 0 fuel when coasting.
AFAIK, any vehicle with electronic fuel injection will do this. I know for a fact the Renix 4.0 (87-90) will cut all fuel under closed throttle conditions above 1200 RPM (I assume it kicks back on at 1200 in case it's dropped out of gear quickly so it doesn't stall). With my manual trans, I can actually feel the injection cut back in when coming to a stop.

Quote:
Originally Posted by WranglerLegend View Post
its impossible to use 0 fuel when coasting, your pistons are still moving, fuel still running through the injectors.
Only with mechanical fuel systems (ie carbed or TBI). The pistons are still moving because they're indirectly connected to the wheels which are being forced to turn by the momentum of the vehicle. This is why engine braking works...It wouldn't work real well if the engine was still getting gas, would it?

Quote:
Originally Posted by RalleyTuned View Post
It is not impossible to have 0 fuel when coasting. Most modern ECU's use what is called "decel fuel cut" which will completely cut the fuel flow to the engine during deceleration. I do aftermarket standalone fuel systems regularly and you can even see on the AFR gauge that it will spike completely lean on decel when you have it setup to do so. I have not calculated the actual difference in having this feature, but it is said to make a decent impact on mpg's.

Are the stock fueling systems on these pretty well tuned? Or are people seeing good power/efficiency gains in switching to programmable systems?
It makes a difference when used properly. I saw around 2 more mpg average when I started engine braking, even just in the city. When driving in really hilly areas, it can be even more (pushed 24 MPG on a trip down from the mountains once )

I would guess the system is tuned for the best balance of power/emissions/mileage. If you were to tune for purely mileage or mileage/power and forget emissions, I'm sure you could do better. But you'd have to know what you were doing to keep the engine running safe.

Willy36 is offline   Reply With Quote
Unread 09-10-2010, 06:38 PM   #17
wiggins48
Registered User
1984 CJ7 
 
Join Date: Aug 2010
Location: mukilteo, washington
Posts: 70
Quote:
Originally Posted by jspb16 View Post
i think i am getting like 12 or 13 mpg! ugh...
Think i'm getting 8 to 10 mpg.It sucks but it's not my dd..My dd is a durango with a 360 as well,get 12 in that.
wiggins48 is offline   Reply With Quote
Unread 11-06-2010, 11:07 PM   #18
Jeffjeep07
Registered User
1997 TJ Wrangler 
 
Join Date: Nov 2010
Location: Eugene, OR
Posts: 2
I drive a 97 TJ and I get around 17-18 with the calculation to count for the odometer being off. I am looking to get a cold air intake and a throttle body spacer and chip to try and get better MPG I just got a job thats 40 miles from home. Any one have intakes, chips or spacers they have had luck with?
Jeffjeep07 is offline   Reply With Quote
Unread 11-07-2010, 12:23 AM   #19
LuckRider
Web Wheeler
 
LuckRider's Avatar
2004 TJ Wrangler 
 
Join Date: Apr 2009
Location: NY - 12550
Posts: 9,308
I am sorry, but have you even taken the time to read the posts? This thread covers those things.

Short answer, save the money. The only thing that will help is better gearing. 4.56 would work well. Better driving too. Honestly, 17 or 18 is pretty good for a 2.5L. They get worse mileage than the 4.0L because they are so underpowered for the vehicle they are pushing.
__________________
Thanks to SuperWade2 For the 1 Year Upgrade!
Support Our Troops!
ALL WK2 Owners, Click Here
JFI Member #7: Helping out the Scammed
2004 Rubi: Ready to Kill the Chrome!
Totaled and Gone: Mostly Stock 2005 I6 Patriot Blue TJ: Monstaliner (Write-Up) BESRK Rear Bumper, Hella 500s
Do the Jeep Wave :D 0|||||||0 Take 95% of what I say as a joke/sarcasm!-Thomas
LuckRider is offline   Reply With Quote
Unread 11-10-2010, 10:04 AM   #20
mmaibachjr
Registered User
1997 TJ Wrangler 
 
Join Date: Mar 2010
Location: Jackson
Posts: 14
I tell you what, i have a '97 sport wrangler and i put a green filter CAI (just took out the box and popped the filter on the end with ties) and put an injen hydroshield on it, as well as a full exhaust from the engine back and I bet i get atleast 18-20 mpg with 33"s and a 4" lift.

I mean the price to effectiveness ratio may not be worth the trouble, but with the 5-speed trans and allowing your engine to breath top-notch, definitely improves fuel economy, or atleast it did for me.
__________________
mike - '97 Wrangler 6cyl. - 4" Skyjacker Lift, 33" Nitto Terra Grapplers, etc
mmaibachjr is offline   Reply With Quote
Unread 11-15-2010, 11:33 AM   #21
pgawrestler112
Registered User
2004 TJ Wrangler 
 
Join Date: Feb 2010
Location: , pa
Posts: 44
Got to love getting 8 miles to the gallon luckly i did the 20 gallon tank conversion
pgawrestler112 is offline   Reply With Quote
Unread 12-12-2010, 02:48 PM   #22
hookuspookus
Registered User
1997 TJ Wrangler 
 
Join Date: Sep 2010
Location: parlin
Posts: 53
i get 27 mpg in my tj
hookuspookus is offline   Reply With Quote
Unread 12-12-2010, 07:13 PM   #23
Willy36
Registered User
1990 XJ Cherokee 
 
Join Date: Dec 2007
Location: FoCo, Colorado
Posts: 1,168
Quote:
Originally Posted by hookuspookus View Post
i get 27 mpg in my tj
no you do not.
Willy36 is offline   Reply With Quote
Unread 12-13-2010, 01:15 AM   #24
hookuspookus
Registered User
1997 TJ Wrangler 
 
Join Date: Sep 2010
Location: parlin
Posts: 53
i'm looking to get 30

[QUOTE=Willy36;10608978] or more .
hookuspookus is offline   Reply With Quote
Unread 01-02-2011, 10:22 PM   #25
tehgregzor
Registered User
2004 WJ 
 
Join Date: Jan 2011
Location: Clarksville, TN
Posts: 94
I get 32 MPG easy....in my xB! I average about 16.8, I just have a 10 minute commute in the city. Not bad, since that's a long running average including heavy foot stop light launches next to h3's, as well as coasting through the local hood to get to my job.
tehgregzor is offline   Reply With Quote
Unread 02-07-2011, 03:11 PM   #26
BuckeyeMac
Registered User
2008 JK Wrangler 
 
Join Date: Oct 2010
Location: Columbus, OH
Posts: 211
Just got my 2000 Auto 4banger TJ mid January. I have about a 17mile drive to/from work both in rush hour downtown Columbus, Ohio so it takes me about 30-40 minutes to get there. I got 17mpg first two fill ups. I'm hoping this will go up to 18-20 once out of the winter months and 22-23 on straight highway driving.

Edit: I'm not complaining just hoping
BuckeyeMac is offline   Reply With Quote
Unread 02-21-2011, 05:24 AM   #27
DieselDreamer
Registered User
1999 XJ Cherokee 
 
Join Date: Feb 2011
Location: Elgin, IL
Posts: 110
Driving habits, Aerodynamics, Engine mods/maintenance.

Driving habits

Driving habits, as mentioned before, are literally key to make things work in your favor with regards to fuel mileage. I'm not just talking about how one throttles the fuel pedal but how one also brakes. I think braking is probably the biggest thing one can alter in order to enhance fuel economy. All that energy is wasted when we brake because we are not driving hybrids with regenerative braking. Save your brakes while saving that expensive fuel in your tank.

Learning to read lights and simply letting off the throttle before braking is a big thing. Sometimes a light turns green, people start moving, and by the time I'm a few car lengths from the car in front of me I may be doing 10mph,20mph,30mph, etc and then get up to speed again. If you are consistently doing 0-45pmh all the time, your wasting fuel. Some English study I read awhile back showed how moving at 10mph constantly is better than stopping and restarting beyond 10mph. I can't source the article at this time but overall it makes sense. I rather be crawling in traffic at 5mph then running through the gears on and off for an hour.

My girlfriend lives in a town with a lot of train tracks. We always hit a train! These are typically not just commuter trains but rather trains that crawl with like 200+ cars on them. Honestly when this happens I just put it in park and shut the engine down... yes even in the winter. Idling is by far the worst form of fuel consumption. When your parked you are getting ZERO MILES PER GALLON. Do the math. Your not moving and your burning fuel thus no miles traveled.

Also, warming your car up in the winter is pointless as well. Especially with these Jeeps! My XJ is up to temperature in less than three minutes of normal driving. http://www.consumerenergycenter.org/myths/idling.html

Aerodynamics

Aerodynamics are key and it shows in fuel mileage tests time and time again. The hand of god (I.E. Physics) will always win! For example, just look at the new Jeeps. If all things were equal, a two door TJ would consume more fuel than a two door JK.

The fact that Jeeps traditional grill has seven slots in it really doesn't help aerodynamics at all. While this is great for low speed trail speeds, it hampers the aerodynamics of the vehicle itself at highway speeds. Air at highway speeds is sucked into the front instead of going around the vehicle. Blocking the holes might be a good idea in the winter months but your Jeep might stay hotter for a longer period of time in the summer months.

Another thing that might seem odd is the antenna is huge. Just look at it at 45+ miles per hour. The thing is wiped back. Shortening it will reduce a small amount of drag on the vehicle while making it look a littler more stylish. Yes your not going to be getting even just one more mpg out of this mod but every little bit helps.

Keeping it at 65mph on the highway is the optimal speed for most vehicles regarding fuel mileage. After that aerodynamics works more against you than with you. One way I literally have fought this is drafting off of semi trucks through the bulk of my destination. I typically do this going to and from my moms house across the state and this trip is roughly 140 miles one way. When I get behind the semis I usually pick out ones that are traveling faster than 55pmh. You can totally tell the wind noise is reduced around you, and at the end of my trip, I get roughly 20-30 miles more per tank. That was on my old car however, so I can't speak for my Jeep. Regardless, I'm sure I will be seeing an increase in mileage per tank following this same process.

Engine mods/mantenance


I always swear by a TRUE cold air intake (CAI) and a decent cat back exhaust. While it doesn't give you more mileage and performance by adding these items it does help give you more mileage and performance by reducing the restrictions these stock items put on your engine. Properly tuning the ECM will help out as well but for cost sake I will omit that option. This items will need to pay for themselves and that honestly could take years of miles driven before any cost return would be seen. Personally, I would just do it for the sound and performance aspect and have the increase in mileage as an added bonus.

Lastly, and probably most importantly, O2 sensors are the biggest thing to check with regards to keeping your fuel mileage consistent. When they go bad the engine typically reads lean and dumps more fuel into the engine. I always check them when I buy a new vehicle. If they are thickly covered in carbon then I replace them. I remember on my Nissan Altima I received a 2mph increase from just changing out the after cat sensor (the back one). If the sensor isn't working right, you will notice it in your fuel mileage. When it comes to maintenance of these sensors I stick to 5 years or 60,000 miles, which ever comes first to change them out.

I think its fair to say things like tires profile,maintained tire pressures, and routine maintenance will really keep your fuel mileage optimal. The only real way to increase fuel mileage is to dump the current motor and go diesel. However, since that isn't in most peoples budget, including me, we can only monitor our driving, pay attention to the aerodynamics of the vehicle, and optimize our vehicle maintenance.

Hope this helps, sorry if I repeated anything. I read most posts before I put this up.

Erik
DieselDreamer is offline   Reply With Quote
Unread 02-21-2011, 05:26 AM   #28
DieselDreamer
Registered User
1999 XJ Cherokee 
 
Join Date: Feb 2011
Location: Elgin, IL
Posts: 110
Quote:
Originally Posted by BuckeyeMac View Post
Just got my 2000 Auto 4banger TJ mid January. I have about a 17mile drive to/from work both in rush hour downtown Columbus, Ohio so it takes me about 30-40 minutes to get there. I got 17mpg first two fill ups. I'm hoping this will go up to 18-20 once out of the winter months and 22-23 on straight highway driving.

Edit: I'm not complaining just hoping
With a three speed, I'm not sure you will be getting 22-23 highway. Just my two cents.
DieselDreamer is offline   Reply With Quote
Unread 02-21-2011, 12:19 PM   #29
Willy36
Registered User
1990 XJ Cherokee 
 
Join Date: Dec 2007
Location: FoCo, Colorado
Posts: 1,168
Quote:
Originally Posted by DieselDreamer View Post
*snip*
Almost all good info, but I have two issues here. Yes the antenna is bent back, but we're talking about a 1lb thin, flexible piece of steel here (as opposed to the 3000-5000lb steel Jeep), you could sneeze on it and it would bend. Snipping the antenna may save you $1.00 on gas every 5 years meanwhile killing your radio reception.

Also, maybe your Altima was different, but I've always been under the impression the post-cat (downstream) O2 sensor was to check the emissions only and had no bearing on air-fuel ratio. I suppose some cars could be different though.

ETA: Make that 3 issues, but with the link you posted, not your info. If you idle for only 30 seconds on mornings below 20*, your engine is going to run like crap because the fuel won't atomize well (thus causing the computer to richen it and....waste gas) and the rings won't be properly seated, thus potentially causing ring blowby. Sure, a cold morning in Florida (55* gimme a break, that's a warm spring day here ) isn't so bad, but in colder climates, you'll want to give a little more time.
Willy36 is offline   Reply With Quote
Unread 02-21-2011, 10:53 PM   #30
DieselDreamer
Registered User
1999 XJ Cherokee 
 
Join Date: Feb 2011
Location: Elgin, IL
Posts: 110
Quote:
Originally Posted by Willy36 View Post
Almost all good info, but I have two issues here. Yes the antenna is bent back, but we're talking about a 1lb thin, flexible piece of steel here (as opposed to the 3000-5000lb steel Jeep), you could sneeze on it and it would bend. Snipping the antenna may save you $1.00 on gas every 5 years meanwhile killing your radio reception.

Also, maybe your Altima was different, but I've always been under the impression the post-cat (downstream) O2 sensor was to check the emissions only and had no bearing on air-fuel ratio. I suppose some cars could be different though.

ETA: Make that 3 issues, but with the link you posted, not your info. If you idle for only 30 seconds on mornings below 20*, your engine is going to run like crap because the fuel won't atomize well (thus causing the computer to richen it and....waste gas) and the rings won't be properly seated, thus potentially causing ring blowby. Sure, a cold morning in Florida (55* gimme a break, that's a warm spring day here ) isn't so bad, but in colder climates, you'll want to give a little more time.
Hey,

Your right about the antenna with out a doubt but every bit helps honestly. If you wanna go nuts you can tape up cracks and seams with strong duct tape. However no one is nerd enough to do it. As for radio, who listens to radio anymore?

I may have replaced the front O2 sensor first. Overall it has been 3 years and I honestly can't remember. Ether way I hated that car so much so I really don't want to remember. I replaced both in the end but when it was all said and done my fuel mileage went up.


Have a good week!

Erik

Last edited by DieselDreamer; 02-22-2011 at 01:16 AM..
DieselDreamer is offline   Reply With Quote
Reply

Tags
faq , gas mileage , improve mpg , miles per gallon , mpg , poor gas mileage
Thread Tools


Suggested Threads





Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.