Optimum speed for mpg and other advice wanted

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

Auberon wrote:

It's curious that no-one has mentioned maintaining / selecting shockers and possibly using tunable ones if you travel over many and varied road surfaces. A tyre that is kept as stable as possible in relation to the tarmac contributes hugely to economy by limiting vehicle jounce, bounce and wheel hopping - stabilising the little brick quickly. A seemingly forgotten factor and very much related to speed of travel / mpg.

i agree. i just put new tires on. they are highway tread and the lightest ones i could find at 28 pounds. they also happened to be the cheapest available. as for shocks, the tunable ones always cost a lot. has anyone done the math to see if the increased mileage would offset the cost?

tjkj2002 · **Posted:** Thu Sep 11, 2014 8:27 pm

npkdm wrote:

Auberon wrote:

It's curious that no-one has mentioned maintaining / selecting shockers and possibly using tunable ones if you travel over many and varied road surfaces. A tyre that is kept as stable as possible in relation to the tarmac contributes hugely to economy by limiting vehicle jounce, bounce and wheel hopping - stabilising the little brick quickly. A seemingly forgotten factor and very much related to speed of travel / mpg.

i agree. i just put new tires on. they are highway tread and the lightest ones i could find at 28 pounds. they also happened to be the cheapest available. as for shocks, the tunable ones always cost a lot. has anyone done the math to see if the increased mileage would offset the cost?

Time to sell the Jeep if your that concerned about mpg's and how long it will take to pay for mods.

Real Jeeps are built not bought and you don't buy a Jeep for mpg's.

thermorex · **Posted:** Thu Sep 11, 2014 9:48 pm

tjkj2002 wrote:

npkdm wrote:

Auberon wrote:

It's curious that no-one has mentioned maintaining / selecting shockers and possibly using tunable ones if you travel over many and varied road surfaces. A tyre that is kept as stable as possible in relation to the tarmac contributes hugely to economy by limiting vehicle jounce, bounce and wheel hopping - stabilising the little brick quickly. A seemingly forgotten factor and very much related to speed of travel / mpg.

i agree. i just put new tires on. they are highway tread and the lightest ones i could find at 28 pounds. they also happened to be the cheapest available. as for shocks, the tunable ones always cost a lot. has anyone done the math to see if the increased mileage would offset the cost?

Time to sell the Jeep if your that concerned about mpg's and how long it will take to pay for mods.

Real Jeeps are built not bought and you don't buy a Jeep for mpg's.

Lol. Very true. Ain't a jeep till you mod something or drill the first hole. Then years later you realize you could have kept one kid in college...

jthomas999 · **Joined:** Mon Jan 16, 2012 11:51 pm **Posts:** 98

Jeep - Just Empty Every Pocket ... :-)

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

not trying to ruffle feathers, but if i wanted a true jeep and wasn't concerned with fuel mileage i would have bought a wrangler.

thermorex · **Posted:** Tue Sep 16, 2014 9:20 pm

I one can't blame you or others from expecting a decent mileage, I think the message was supposed to send the idea that a jeep, with few offroad capabilities like a stock kj, will never get the mileage of a jetta tdi. Even all wheel drive golfs in Europe have few litters/km worse mileage than the fwd wheel drive ones. Plus they have better aerodynamics. What puzzles me is the huge discrepancy between several jeep drivers, and also the discrepancy I get sometimes, worse highway was about 23, best was a bit over 30. I always put this on the tire pressure, winter weather, wind, fuel quality etc. I get way more consistent mileage with my 4.0 Cherokee, that hovers around 17.5 winter or summer, windy or not...

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

I thought i should report my findings on the best speed for mpgs. i drove my rig almost two years and the best i saw was 32 mpg on the computer readout. i know it reads high but i'll use it for comparison. this summer i tried driving as slow as the liberty would go in OD with the coverter locked up. that is 57 mph in my rig. the readout climbed to 42 mpg. so i have concluded that it might be beneficial to regear and drop my rpms. it might help.

Dent · **Joined:** Sat Aug 04, 2012 11:05 pm **Posts:** 275

I have GDE eco and Weeks 1 and 2. 4" JBA with Goodyear Wrangler MTR Kevlar 32 x 11.5 x 15. I get 19-20 mpg. I mostly drive back and forth to work with a 2500' elevation change usually under 50 mph. Before the lift and tires, I would see 24-25 mpg.

flash7210 · **Posted:** Fri Sep 09, 2016 12:15 pm

npkdm wrote:

I thought i should report my findings on the best speed for mpgs. i drove my rig almost two years and the best i saw was 32 mpg on the computer readout. i know it reads high but i'll use it for comparison. this summer i tried driving as slow as the liberty would go in OD with the coverter locked up. that is 57 mph in my rig. the readout climbed to 42 mpg. so i have concluded that it might be beneficial to regear and drop my rpms. it might help.

Regear to what?
There are several options for the rear axle but for the front diff there is only 3.73 (stock) and 4.10.
If you are willing to get rid of your front axle components then you could definitely install a numerically lower gear set in the rear.

You may want to consider switching to a 2005 Ram Hemi TCM. It's shift pattern is very different but it will allow you to get into 5th gear at 50 mph. Of course it won't change your gear ratios though.

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

CATCRD wrote:

The optimum speed for mpg is as slow as you can go in top gear with these KJs. They are just not aerodynamic.

I think that's the best advise as for speed.

I get my best number by getting the RPM as low as possible on 5 gear lock up !!!!!!
I wish I have a trans tune from GDE !!!!!!

For the mods I think the electric fan and eco tune are the most important one for fuel economy.

And I can wait to see the effect of the Webasto heater on the MPG in the winter.

npkdm · **Joined:** Wed Sep 03, 2014 8:28 pm **Posts:** 163

flash7210 wrote:

npkdm wrote:

I thought i should report my findings on the best speed for mpgs. i drove my rig almost two years and the best i saw was 32 mpg on the computer readout. i know it reads high but i'll use it for comparison. this summer i tried driving as slow as the liberty would go in OD with the coverter locked up. that is 57 mph in my rig. the readout climbed to 42 mpg. so i have concluded that it might be beneficial to regear and drop my rpms. it might help.

Regear to what?
There are several options for the rear axle but for the front diff there is only 3.73 (stock) and 4.10.
If you are willing to get rid of your front axle components then you could definitely install a numerically lower gear set in the rear.

You may want to consider switching to a 2005 Ram Hemi TCM. It's shift pattern is very different but it will allow you to get into 5th gear at 50 mph. Of course it won't change your gear ratios though.

i haven't looked into the re-gearing at all. I was unaware there are no choices available to put a taller gear in the front end. my thinking was that some 3.42 or 3.08 gears would increase mileage. taller tires could drop my rpms but they will be heavier than the tires i have now. so it could be a wash or even hurt my mileage. my current tires are 235/70r16 and have a shipping weight of 29 pounds. these are pure street tires though. I have been looking for a light weight AT tire and haven't found one under 38 pounds.

also what is a webasto heater?

95Z28A4 · **Joined:** Sun Mar 30, 2014 9:53 am **Posts:** 297

npkdm wrote:

i haven't looked into the re-gearing at all. I was unaware there are no choices available to put a taller gear in the front end. my thinking was that some 3.42 or 3.08 gears would increase mileage. taller tires could drop my rpms but they will be heavier than the tires i have now. so it could be a wash or even hurt my mileage. my current tires are 235/70r16 and have a shipping weight of 29 pounds. these are pure street tires though. I have been looking for a light weight AT tire and haven't found one under 38 pounds.

3.55 gears are available.

I have installed 235/75/16 Firestone Destination ATs on my wife's CRD. They are 29.8" in diameter and nearly correct the speedometer error. They are an "S" rated all terrain and weigh 35 lbs. I run them at 40 psig air pressure. The Destination ATs are quiet (very quiet for an all terrain tire) and have lasted 50k - 60k miles for me. I have run BFG T/A KO all terrian tires on some of my other vehicles. I liked them because they have an aggressive tread and they last, but are heavier and noisier than the Firestone Destination ATs. The 245/75/16 Firestone Destination ATs are 30.5" in diameter and weigh 38 lbs. When buying all terrain tires in sizes that fit our CRDs, be aware that some manufacturers sell the tires with passenger car ratings (P - S/T speed rated) and light truck ratings (LT - C/D/E load rated). The light truck all terrain tires will be more durable, have stiffer sidewalls and will be heavier. On my old Cherokees, I ran light truck tires for the thicker side walls and improved puncture resistance for off-roading. With the CRD, I run passenger car rated tires because I am more concerned with fuel economy, than off-roading.

TURBO-DIESEL-FREAK · **Joined:** Sat Apr 17, 2010 3:29 pm **Posts:** 1167

npkdm wrote:

flash7210 wrote:

npkdm wrote:

I thought i should report my findings on the best speed for mpgs. i drove my rig almost two years and the best i saw was 32 mpg on the computer readout. i know it reads high but i'll use it for comparison. this summer i tried driving as slow as the liberty would go in OD with the coverter locked up. that is 57 mph in my rig. the readout climbed to 42 mpg. so i have concluded that it might be beneficial to regear and drop my rpms. it might help.

Regear to what?
There are several options for the rear axle but for the front diff there is only 3.73 (stock) and 4.10.
If you are willing to get rid of your front axle components then you could definitely install a numerically lower gear set in the rear.

You may want to consider switching to a 2005 Ram Hemi TCM. It's shift pattern is very different but it will allow you to get into 5th gear at 50 mph. Of course it won't change your gear ratios though.

i haven't looked into the re-gearing at all. I was unaware there are no choices available to put a taller gear in the front end. my thinking was that some 3.42 or 3.08 gears would increase mileage. taller tires could drop my rpms but they will be heavier than the tires i have now. so it could be a wash or even hurt my mileage. my current tires are 235/70r16 and have a shipping weight of 29 pounds. these are pure street tires though. I have been looking for a light weight AT tire and haven't found one under 38 pounds.

also what is a webasto heater?

A Webasto heater is a diesel fueled engine coolant heater. The one that PZKW108 has - a Webasto TSL17 - is capable of warming up a 3500 lb commercial diesel engine. In diesel powered passenger vehicles and pickup trucks, a TSL17 will heat up the engine to about 170 degrees Fahrenheit in less than 45 minutes with no electrical outlet required... you can also remotely start them. With a Webasto TSL17 heater, you will have a device that is capable of 12.5 times the power of your engine block heater.

Webasto heaters will save you fuel, because they are very efficient; especially so compared to an idling diesel engine. This will also save you wear and tear on the engine and fouling of the engine oil. Using a Webasto will also keep your engine warm in areas that prohibit engine idling, like hospitals.

WWDiesel · **Posted:** Sun Sep 11, 2016 11:13 am

If you are wanting high fuel mileage, go buy yourself a VW diesel! The Jeep Liberty Diesel is a heavy boxy non-aerodynamic SUV and as such, no matter what you do, will never achieve super great fuel mileage consistently.... :roll:

With all the mods and different tuning, I have been able to squeeze about 35 to 37 mpg out of mine under certain very controlled driving conditions, but that is certainly not the norm for this vehicle...
The key to good mileage with this vehicle is controlled consistent speeds, open exhaust (no CAT & straight through muffler), clean air filter, and very mild acceleration when required... :mrgreen:

ps. I am running 245/75/16 mild AT tires @ 37 psig.

flash7210 · **Posted:** Sun Sep 11, 2016 12:27 pm

Quote:

I have been able to squeeze about 35 to 37 mpg out of mine under certain very controlled driving conditions...

... downhill with a strong tailwind :-)r

Myself, i get 23mpg. City and highway.
Been this way ever since I got AT tires.

WWDiesel · **Posted:** Sun Sep 11, 2016 2:31 pm

flash7210 wrote:

Quote:

I have been able to squeeze about 35 to 37 mpg out of mine under certain very controlled driving conditions...

... downhill with a strong tailwind :-)r

Myself, i get 23mpg. City and highway.
Been this way ever since I got AT tires.

Not quite, but very consistent controlled driving conditions... No tailwind and downhill 100% of the time! :ROTFL:

Best I have seen in town stop & go driving is about 27 mpg...

thermorex · **Posted:** Sun Sep 11, 2016 4:38 pm

npkdm wrote:

flash7210 wrote:

npkdm wrote:

I thought i should report my findings on the best speed for mpgs. i drove my rig almost two years and the best i saw was 32 mpg on the computer readout. i know it reads high but i'll use it for comparison. this summer i tried driving as slow as the liberty would go in OD with the coverter locked up. that is 57 mph in my rig. the readout climbed to 42 mpg. so i have concluded that it might be beneficial to regear and drop my rpms. it might help.

Regear to what?
There are several options for the rear axle but for the front diff there is only 3.73 (stock) and 4.10.
If you are willing to get rid of your front axle components then you could definitely install a numerically lower gear set in the rear.

You may want to consider switching to a 2005 Ram Hemi TCM. It's shift pattern is very different but it will allow you to get into 5th gear at 50 mph. Of course it won't change your gear ratios though.

i haven't looked into the re-gearing at all. I was unaware there are no choices available to put a taller gear in the front end. my thinking was that some 3.42 or 3.08 gears would increase mileage. taller tires could drop my rpms but they will be heavier than the tires i have now. so it could be a wash or even hurt my mileage. my current tires are 235/70r16 and have a shipping weight of 29 pounds. these are pure street tires though. I have been looking for a light weight AT tire and haven't found one under 38 pounds.

also what is a webasto heater?

Keep in mind that lower gear ratio will add more load on the engine which increases fuel consumption, unless you modify your driving habits to barely accelerate. It's similar to replacing your stock tires with bigger diameter tires. Load increases on same time 0-60 acceleration, but you gain higher speed per rpm. So regearing won't necessarily increase your mileage, unless you adjust the way you accelerate.

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

WWDiesel wrote:

If you are wanting high fuel mileage, go buy yourself a VW diesel! The Jeep Liberty Diesel is a heavy boxy non-aerodynamic SUV and as such, no matter what you do, will never achieve super great fuel mileage consistently.... :roll:

With all the mods and different tuning, I have been able to squeeze about 35 to 37 mpg out of mine under certain very controlled driving conditions, but that is certainly not the norm for this vehicle...
The key to good mileage with this vehicle is controlled consistent speeds, open exhaust (no CAT & straight through muffler), clean air filter, and very mild acceleration when required... :mrgreen:

ps. I am running 245/75/16 mild AT tires @ 37 psig.

The Liberty CRD does pretty good for a heavy boxy non-aerodynamic SUV with good off road and towing capability.

How many mpg you think the muffler and cat will yield ??? muffler might be my next step !!!

WWDiesel · **Posted:** Sun Sep 11, 2016 9:50 pm

PZKW108 wrote:

The Liberty CRD does pretty good for a heavy boxy non-aerodynamic SUV with good off road and towing capability.
How many mpg you think the muffler and cat will yield ??? muffler might be my next step !!!

Blanking off the EGR system or installing a Weeks elbow kit, which also gets rid of the whole EGR system, along with removing the CAT and the choke point in front of it and adding a straight through muffler or no muffler at all if you do not mind the noise should yield you about 3 or 4 better mpg's... :mrgreen:

Removing the choke point and CAT and installing a free flowing straight through muffler will also lower EGT's and shorten turbo response time due to the lower exhaust back pressure... And of course it sounds so much better with a little rumble... :-)r

ps. Removing the CAT completely will not set any DTC's (trouble codes) as there are no O2 sensors on this vehicle... Many on this list who have removed their CAT have reported still passing inspection if required in your area!!!!

mass-hole · **Posted:** Mon Sep 12, 2016 12:18 am

flash7210 wrote:

Quote:

I have been able to squeeze about 35 to 37 mpg out of mine under certain very controlled driving conditions...

... downhill with a strong tailwind :-)r

Myself, i get 23mpg. City and highway.
Been this way ever since I got AT tires.

I used to average 29 mpg with the stock tires and gde hot tune, and would regularly get 34 hwy. Once or twice I got 36.

Now I average 25 but don't see much better on the hwy. I will say that when I took the stock cooling fan off for a few days I was seeing 29-30 mpg which I have not seen since last July when the duratracs went on. It was a very dramatic increase, so I don't think it was just a fluke.

Optimum speed for mpg and other advice wanted

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