MPG updates

[06JeepXKHEMI]

Just checking with other HEMI owners out there.. Before I installed the CAI I was avg 10-11mpg, all city driving. After the intake I was at 12.2-13 all city and was for awhile.. Now Im avg 10.5 at best, Im thinking its the heat but curious to see what others are getting. I do have a heavy foot but to drop that much with the same driving????? No codes, new OEM plugs, any ideas or is everyone else close to this during the summer

[pjmjr508]

I avg 10 - 11 98% city Kinda heavy foot

[Matt]

I get 12-13 with a relatively light foot for my city driving. Sometimes I'll see mid to high 13s when cruising 50-60 mph on some back roads.

I don't see 10 unless im towing or offroading...

[07JeepXK]

My friend Bob who just got the 06 HEMI XK a few weeks ago called me last night. A few days ago he swapped out the spark plugs with oem champions purchased from the dealer. He said that the plugs he pulled out were the same part number as the ones he put in and that they looked like they were original from the factory. His XK has 72,000 miles and the plugs that came out were shot with a gap of .060+. The new plugs were gapped according to the sticker under the hood and he said his Hemi runs so much stronger now but at the same time his MPG has dropped down significantly. The only change was the new plugs.

Now im not an expert on this but is it possible that the engine learned the gap of the old plugs and is now dumping more fuel to make up for the new plugs and better spark? Maybe the PCM just needs to relearn everything now with the new plugs.

[06JeepXKHEMI]

Not sure, but I was talking with my Dad this weekend about our computers and what not.. Although they need to "relearn" at times, they are sensitive to the driver itself. For instance, when I accelerate even if not WOT it will accelerate almost like WOT per my driving habits its learned. Its possible it reads a better spark and cause of his driving habits its dumping more fuel in to accommodate the better spark, but Im trying to figure out why mine as dropped with no change to the XK at all. Im guessing just how heavy my foot is but Ive been nursing her around and my mpg is going down! Maybe a good question is what fuel type are people using and which gas station?? I wish there was a race trac around here I always got waaay better mpg with their fuel..

[07JeepXK]

What octane are you using? I wouldnt go over 91. Thats what I run and have flashpaq tuned to 91 performance. Bob uses the same octane on same tune.

[06JeepXKHEMI]

I dont have a tune and Ive been doing 87 or 89 and saw real no difference. Next fill up I will do 91, best mpg came from Sunoco which is what Im running now 87 so I will go up to 91 or 93.

[07JeepXK]

I thought that its recommended to run a minimum of 89 octane in the Hemi's??

[06JeepXKHEMI]

I thought so but it doesnt say anywhere on gas cap or owners manual. I think only the str8 HEMI's require minimum octane

[Matt]

My 07 owners manual recommends 89 octane. It says 87 can be run if no knock s experienced and that 91+ is not recommended for use.

After any mod or engine maintenance like spark plugs its a good idea to disconnect the battery. The computers do "learn", but disconnecting the battery puts it directly into an accelerated learn mode. After a period of driving time the algorithm slows so it takes changes to the system longer to propagate.

[07JeepXK]

91 Octane wont hurt anything though if your running a 91 tune through superchips. I have been running either 91 or 93 octane in my 4.7 XK for over 3 years now with now problems. Well beside the hole it makes in my wallet.

[06JeepXKHEMI]

the HEMIs have to be careful tho with the higher octanes, Im wondering tho if Im losing performance and mpg due to pre-ignition???? Seems to be an issue after researching this is a common topic. I didnt buy my XK for fuel economy but the sudden drop was concerning, Im going to start with 91 and see how it runs... This is going to be an expensive guess and check game

[Matt]

I use Shell and Sonoco 89 by me.

If you've been switching between 87 and 89, try sticking with 89 for a few tanks so the computer isn't constantly trying to adjust between tanks.

[06JeepXKHEMI]

Ok Ill do 89 then for a few and see what happens. Still doesnt explain the sudden drop but oh well. No codes, no lights no problem.. I hope!

[Matt]

My memory is escaping me.... how many miles are on it and do you know when the plugs were last change? I noticed a stark decrease in mpg as I approached 30k on my plugs.

[Matt]

Maybe disconnected the battery for the hell of it too.

[06JeepXKHEMI]

Ive got 79k and only 2500 miles on the plugs, just did complete 60k service-all fluids plugs front diff bushings belts- when I purchased. I will disconnect the battery to see how that helps...

[06JeepXKHEMI]

I disconnected the battery for a min to reset the computer, I will update to see if that does anything...

[Sal-XK]

I hit 17-18 MPG coming this last weekend 6 people plus luggage and both front and rear AC on I did however have my basket and cross bars off. Running no tune just corrected for tire size and on 87 octane.

[Matt]

Literally a minute? Needs like 10-15 for memory to reset (I turn the key on for good measure too)

[06JeepXKHEMI]

Not literally a minute, everything was set back to 0, mpg, time running, etc.. Ill go to it for longer but everything seems to be cleared

[Matt]

Lol got it

[Core XK]

I have been running 87 since I've had my XK so maybe I will try 89 next fill up? The only mods I've done to the engine so far is put the K&N drop in air filter which I feel improved but then the tires and lift went o,n and I am down to an average of 12-12.3 city driving mostly.

[06JeepXKHEMI]

Thought Id give an update, after switching to Sunoco 89 for 87 mpgs went up and are now at 11 from 9.8-10.. Still a huge drop from before this issue came about, 12.2, but I didnt buy her for gas mileage!!! And yes you should switch to 89 as per factory recommendations..

[Core XK]

Thought Id give an update, after switching to Sunoco 89 for 87 mpgs went up and are now at 11 from 9.8-10.. Still a huge drop from before this issue came about, 12.2, but I didnt buy her for gas mileage!!! And yes you should switch to 89 as per factory recommendations..

Okay, I think I will do the switch and let it get to E then fill it w/ 89 :)

[AJeepZJ]

I know this post was originally targeting HEMI's. But for you V6'ers. I just wanted to update that I haven't reset my mpg in almost 2 months, my combined MPG's is still going up. I'm getting 16.5.

[Matt]

Okay, I think I will do the switch and let it get to E then fill it w/ 89 :)


Don't forget your odometer & speedometer are going to be off due to the tire size change. Until that's corrected, your "mpg" reading will be lower (you'll be traveling further than the computer thinks due to the increased tire diameter)

[Core XK]

Don't forget your odometer & speedometer are going to be off due to the tire size change. Until that's corrected, your "mpg" reading will be lower (you'll be traveling further than the computer thinks due to the increased tire diameter)

Yeah I forgot about that. The only way to really "correct" this is by a tuner? :/

I still will change to 89 if its better fuel for the hemi

[Matt]

yeah you'll Want a tuner eventually to correct the tire size. Definitely run 89 in that Hemi

[Core XK]

Sucks I just filled up with 87 but after this weekend I will need to fill it again lol

I will be getting a tuner eventually :O

[Sal-XK]

Been driving a lot with lots of idle time still getting 15.6 right now mixed city/hwy

[06JeepXKHEMI]

What kills me is I drive MAYBE 5-10 miles a day all city no highway, plus I dont have the updated tire size in the computer so it a little off as Matt said it would be

[Sal-XK]

What kills me is I drive MAYBE 5-10 miles a day all city no highway, plus I dont have the updated tire size in the computer so it a little off as Matt said it would be

I ran a year before I got the sc programmer and it was about a 2MPG gain after the correction. That was running the 265's

[06JeepXKHEMI]

WOW! Im not that optimistic but gaining 2 mpg would be nice, thatd be 13mpg city!!! pretty sad when we HOPE for 12.5-13 hahaha

[Core XK]

WOW! Im not that optimistic but gaining 2 mpg would be nice, thatd be 13mpg city!!! pretty sad when we HOPE for 12.5-13 hahaha

Yeah after skids a programmer may be my next purchase

[valpacer]

The minimum octane down here is 91, so i dont think it should be an issue in a Hemi.

Greg (mate of mine who has an 07 Hemi, same saguaro front bar and rear bar) got on his last melb-bris-melb trip (round 4000km trip) he averaged 16l/100km (14.7mpg) on std 91 octane, no tune. Mixed use, some offroad, some beach, some city, some highway.

Wont be an issue for him, he has just bought a CRD and all the gear is being transferred.

I wont mention that i got 10.1 l/100km (24mpg) average over the last 2 trips, including offroad use. Ooops, just did.:D Just doesnt sound as good as a Hemi does under load up a nice long hill.........

[06JeepXKHEMI]

Oh the pleasures of a diesel!! Yea it may not sound like a HEMI but that fuel economy is awesome, only if an inline 6 Cummins could have came under the hood, hhhhmmmmm!!!! To update my mpg's the last trip to Rausch Creek I avg'd 15.3-15.5 on the way down (hwy) and 15.4 on the way home, by far the best I ever have had. I was using Sunoco 89 and will continue to as it seems to run the best with their gas. It will be interesting to see what my city mpgs stay at...

[lekmedm]

The minimum octane down here is 91, so i dont think it should be an issue in a Hemi.



I've read that the way octane is calculated is rather region specific. There is no international agreed standard for doing the math.

In Europe there is 95 and 98 octane unleaded. The 95 octane actually corresponds to 87 octane in the USA.

[07JeepXK]

I've read that the way octane is calculated is rather region specific. There is no international agreed standard for doing the math.

In Europe there is 95 and 98 octane unleaded. The 95 octane actually corresponds to 87 octane in the USA.

So does that mean if he is running 91 octane he is actually using an octane less then 87?

[valpacer]

I've read that the way octane is calculated is rather region specific. There is no international agreed standard for doing the math.

In Europe there is 95 and 98 octane unleaded. The 95 octane actually corresponds to 87 octane in the USA.

Ahhh, i didnt know that.

We have 91 as standard, 95 Premium, 98 Optimax, and then some now have 100octane. Dont know what they match up to but the 98 optimax with Toluene was a match for Avgas back when i had the drag car.

[Pixelcodex]

Wont be an issue for him, he has just bought a CRD and all the gear is being transferred.

I wont mention that i got 10.1 l/100km (24mpg) average over the last 2 trips, including offroad use. Ooops, just did.:D Just doesnt sound as good as a Hemi does under load up a nice long hill.........

Hello Dave, I bought my WK CRD used and with quite a few miles, but never got better than ~17 average hand calculated (EVIC shows 15.4 - 16), though I use it mostly for commuting now, so it is city driving. What kind of mileage did you get before the GDE tune? Is this hand calculated or EVIC? Did you do any corrections after getting the larger tires, etc? If so, what tool did you use? I have never heard that good an average, even from other CRD guys in the states. Do you think the diesel formulation is somehow different down under as well? Thanks.

[jjt250]

Hello Dave, I bought my WK CRD used and with quite a few miles, but never got better than ~17 average hand calculated (EVIC shows 15.4 - 16), though I use it mostly for commuting now, so it is city driving. What kind of mileage did you get before the GDE tune? Is this hand calculated or EVIC? Did you do any corrections after getting the larger tires, etc? If so, what tool did you use? I have never heard that good an average, even from other CRD guys in the states. Do you think the diesel formulation is somehow different down under as well? Thanks.

I don't wanna speak for Dave but I don't think he has a DPF either. As far as tire size correction goes, I think you can get a Hypertech tire re programmer and also I think the AEV EGR (From the Superlift, but you can also buy separately) can reprogram tire sizes as well as ESC for larger tires.

[Pixelcodex]

I don't wanna speak for Dave but I don't think he has a DPF either. As far as tire size correction goes, I think you can get a Hypertech tire re programmer and also I think the AEV EGR (From the Superlift, but you can also buy separately) can reprogram tire sizes as well as ESC for larger tires.

Correct, in Australia, they came with one from 2010 on. I will look into those programmers.
Edit: Hypertech does not list it for the CRD engine, and I know I saw the AEV on their site before, but can't find it now under WK stuff.

[valpacer]

Correct, I have no DPF, and use the AEV EGR module for tyre size calibration. My mileage was always pretty good, but even the change to a 265/70 will throw the calculations off.

As a comparison, Stu's WH with a 3" exhaust, no snorkel and only rock rails only gets an average of 12l/100km, but it also rarely sees 100km/h, doing the school and shopping runs. Wherever I go i have to travel at least an hour by highway so thats also a factor.

[LWM]

Getting 50 + MPG on vacation :)

[07JeepXK]

It doesn't count if your tires are smaller then 20 inches tall.. Lol

[Matt]

And your engine fits in my lunch box..

[jjt250]

Correct, in Australia, they came with one from 2010 on. I will look into those programmers.
Edit: Hypertech does not list it for the CRD engine, and I know I saw the AEV on their site before, but can't find it now under WK stuff.

I could be wrong but I think they make a programmer just for tire re programming. Not engine specific but I might be wrong.

[valpacer]

I know SuperChips does not work on the CRD models at all, even for tyre change size, so check before you buy!

[Core XK]

And your engine fits in my lunch box..

LOL

[brendon]

I ran a year before I got the sc programmer and it was about a 2MPG gain after the correction. That was running the 265's

I could be wrong, but I don't think running with the tire correction changes real world MPG, just the way you (or your EVIC) figure it out.

If you are running uncorrected, the car travels farther than what the odo is reporting, for example it may report a trip of 200 miles. Do the correction and now the exact same trip will show on the odo as 250 miles. Say you used 20 gallons on each trip; according to the math the first trip you got 10mpg, but on the second trip you got 12.5mpg. Real world this trip distance as measured by a survey crew could be 230 miles giving a real MPG of 11.5 for both trips. The trip distance and fuel usage did not change, just the factors used to figure out the mileage.

Now, if the computer uses different cal factors for tire size to alter the way the Jeep puts the power to the road, then all bets are off...

[Sal-XK]

I could be wrong, but I don't think running with the tire correction changes real world MPG, just the way you (or your EVIC) figure it out.

If you are running uncorrected, the car travels farther than what the odo is reporting, for example it may report a trip of 200 miles. Do the correction and now the exact same trip will show on the odo as 250 miles. Say you used 20 gallons on each trip; according to the math the first trip you got 10mpg, but on the second trip you got 12.5mpg. Real world this trip distance as measured by a survey crew could be 230 miles giving a real MPG of 11.5 for both trips. The trip distance and fuel usage did not change, just the factors used to figure out the mileage.

Now, if the computer uses different cal factors for tire size to alter the way the Jeep puts the power to the road, then all bets are off...

You went over board on that man LOL real word mileage never changes. I was and was assuming everyone else was just reporting what the computer calculated which is off by 10% uncorrected. Now I did take the reported mileage and divide by gallons used then corrected for the error to get my actual mileage. I wasn't saying that I actually gained 2MPG real results by correcting but more that's the difference in the tire size error you get. Just pretty much telling the guy with the uncorrected speedo to add about 2 to his reported MPG so he had an idea of his actual MPG.

[Core XK]

After my lift and tires im at 12.9 to 13.2 according to my evic. I have a light foot and was getting 13.5 to 14 prior (city driving). A lift and tires will get you less mpg if im not mistaken ;p?

I stopped looking at my evic because I just dont.care anymore LOL

[06JeepXKHEMI]

Im at 12.3-12.5 with a lead foot and the sounds of the HEMI with the intake and exhaust is orgasmic!!! Lift, tires, added weight from skids will all affect mpg, but as long as its not 9.6 like I was getting before Im good with it

[Core XK]

lol Yeah 9.6 is pretty bad

[Sal-XK]

I'm at 15.9 right now

[06JeepXKHEMI]

After driving to gym/lunch, Im down to 12.2 cause its nice and cool out, so I was stretching the legs on her a bit!!! Interested in how the headers and possibly high flow cats will affect this... honestly I wont care!!!

[brendon]

No worries Sal. I hope you didn't take it as I was picking on you. Your reply I quoted just happened to be the most straight forward as a demonstration of how this COULD be misleading.

I don't want people to think that they are actually getting better mileage because their evic tells them so after a calibration for tire size. Unless of course that makes them feel better about our 'terrible' mileage in these trucks in the first place.

Anywho..
According to fuelly.com, I am averaging 11.5mpg. This is using trip miles that the jeep is reporting; the dealer supposedly calibrated for my larger tires 4 years ago. I have checked out the odo compared to my GPS and it is pretty close. I have noticed that when my speedometer reports 40mph, I am actually going about 40mph; unlike most cars with stock size wheels and tires where the speedo (and odo) report a little higher than actual.

[Sal-XK]

Nope no worries here man :) I hope people know I was just quoting the error pretty much and how much it was off.

[superacerc]

I'm getting about 15.5 hwy(65mph) now 14 mixed and 11-12ish city with the 91oct tune from superchips. I'm pretty happy with that. Bet I could be 16 something hwy without my rack on top.

[pjmjr508]

245 miles each over the weekend got 13.9 mpg flashpaq 91 W/MDS on

for 2 days of straght of wheeling 1 tank of gas @ 8.2 MPG

had a blast

[06JeepXKHEMI]

Took my parents (2) and sister's family (2 1/2) to the state fair, way there got 15.4 on 89 Sunoco, way back was heavier on the foot got 14.1..

[peteyturbo]

I think we have different definitions of "city" driving. And also when you "correct" for your tire size with a programmer it is probably still wrong.. Tire dimensions vary by a huge amount between mfr's of the same size. I corrected for my tire size with the diablosport intune and it was still not right after being verified by gps..I get an honest 8.9 to 10.5 miles per gallon in the city without even having a heavy foot. I live where there are stop signs or red lights at every city block, not just the ocasional stop and 30mph cruise. It just too much weight to be throwing around constantly lol..
However, I did see some improvement after custom tuning the car. I have the stoich AFR set a bit leaner with a bit more timing added in light load areas, mds hangs in a bit longer then normal (aka stays active up to a lower vacum limit), and I was also able to modify the shift points going up to 3rd gear for all throttle settings as well as downshifts too. Combine this with 40psi of pressure in the tires I was able to finally get what I thought was "acceptable" mileage on the highway.. I drove from Philadelphia to Outer Banks and had an average of 16.3 with a turtle shell on the roof before I hit the sand, and I would consider that 60% highway. After that I went from Philadelphia to Allentown ~80 miles each way and got 16.9 going north and 18.0 going south trying to conserve fuel for the most part.
Specs on the commander are 3 row seating,2006 limited Hemi stock ride height with surefoot pandas, AFE intake, MBRP 3" exhaust, and a custom tune I did.
The best part is, I was towing my friends Volvo XC90 6 miles through the sand @OBX in 4wd low and was getting 3.4 miles per gallon doing about 15mph.. The jeep performed flawlessly on the sand aside from my blown out shocks and struts.. I really need to decide what to put on as far as a lift goes...

[06JeepXKHEMI]

Made the trip to Pittsburgh and back to watch a great victory!!! Avg'd 15.6 on the way down Sunoco 89 and 15.9 on Giant/Eagle Value gas, very surprising. Didnt know the area so I didnt want to go to far without getting gas. I just got the DiabloSport Intune so Ill be updating what that does for me..

[06JeepXKHEMI]

Made the move yesterday in the am, was moving pretty good about 80-85 and with the new tune on Sunoco 91 I avg 16.4!!! I will update on how my city mileage works out but Im assuming if I were going normal speeds, 70-75 Id be at 17 or above.