Optimum speed for mpg and other advice wanted

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

I'm a new crd owner and want the best mpg I can get. I have been reading in different threads here about other peoples fuel mileage. One guy will say he gets 25 on the highway and another guy will fire back with his 28-30 while driving 80 mph on the highway. I have found that I get 23 mpg at 70 mph (25 mpg on the computer readout) and I can get 30 mpg (33 by the computer) if I keep it below 65. Have any of you determined the optimum speed for fuel mileage? I would like to hear about it if you have.

Also, I am interested in any mod that improves mpg. I am not real familiar with the computer tunes you can get, is one better than another? Is there more than one offered? It already has the elephant hose mod from the PO and he recommended that I unplug the sensor on the airbox ( MAF I think) so I did. I don't think is has had the f35 recall program put on it (I did the accelerate to 60 and hold test mentioned here in another thread).

I am interested in a lift kit to get more ground clearance, how much will it hurt mpg? If it will kill mpg I won't do it. Is there a possibility that taller tires could improve mpg by changing the relative gear ratio? It seems like my rigs turns the same rpm's at 60 mph that a gas burner does.

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tjkj2002 · **Posted:** Thu Sep 04, 2014 11:36 pm

Lifting it will lower mpg's as will increasing tires size.Go the speed limit and be happy.

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

How much mileage will I lose if I lift it? I don't do any serious off-roading but extra clearance would be nice when driving on field roads.

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Gageraid · **Posted:** Fri Sep 05, 2014 1:26 am

npkdm wrote:

How much mileage will I lose if I lift it? I don't do any serious off-roading but extra clearance would be nice when driving on field roads.

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Lifting it won't kill the mpg's, the LARGER/HEAVIER tires will.
Mine is lifted a little over 2 inches and I didn't lose anything drastic, maybe .5mpg at most.
Once I threw on some A/T tires (same size as stock) I lost close to 2 mpg.
*I track my mileage religiously.

Lancer · **Posted:** Fri Sep 05, 2014 3:07 am

Firstly, you have to accept that "good" mileage on our vehicle is relative. I have a 2" OME lift and it reduced mileage by about .5 mpg, maybe a bit more, but the increased clearance on rough tracks was well worth it. Larger and heavier tyres will hit it much more. Road biased tyres will be better for your mpg than offroad biased.

The Green Diesel tune is probably the best "off the shelf" CPU tune for economy and driveabilty and is happily used by many in the US and Australia. I'm the only one I know of in the UK who has it, but there may be more:) This improved my overall mpg by about 10 -15%; better on cruising, but still an improvement in slow and heavy traffic.

The next mod that was very mpg friendly was a stainless steel Vortex exhaust. Quicker pickup, quieter and an improvement of about 5 - 10% - again better effect at steady-speed cruising, not so noticeable at low speed crawling.

I have a snorkel, but that seems to be largely mpg- neutral, however it does keep the airfilter a lot cleaner. I'd say the filter had only half the filth (if not better) for the year after fitting than before.

I've just had the Sasquatch EGR delete kit fitted, and the elbow that was removed was heavily restricted with goop. I've yet to run it any distance, so I don't yet know what effect it will have on economy.

Carry as little weight in the vehicle as you need. If you carry your entire tool kit, floor jack, enough spares to rebuild the engine and drivetrain and half a dozen jerries of fuel, your mpg will be hammered.

Light foot on the accelerator, use brakes as little as possible (consistent with safety) and regular servicing with good oils and filters, will do a lot for fuel economy. As for cruising speed, keeping rpm in the 1800 - 2200 range seems to be the sweet spot for me.

I'm not the best qualified to comment and there are a lots of lads on this forum who know way more than me, so read the forum (especially the Noob guide) and you will get a lot from it. I have owned my CRD since 2006 and use it regularly. We tour in Europe in it, and love it.

Hope this helps.

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

Read up on the Green Diesel Engineering Eco Tune. Not cheap, but a good investment.

If you don't mind a little more exhaust noise, try a high flow muffler. I have a aeroturbine on mine, others have just removed their muffler and straight piped theirs.

The EcoTune will reduce the EGR function to almost 0, but will not turn on the Check Engine Light.

The EGR delete will remove your EGR, so keep that in mind if your area does smog testing.

John

jeepdan · **Posted:** Fri Sep 05, 2014 7:50 am

You wont see any better without a tune from GDE, simple as that.

But, with a GDE Eco tune, stock size tires inflated to 38psi, stock exhaust and brakes that aren't dragging.

27-28mpg for everyday driving, 30-31mpg interstate (under 70mph), 17.5mpg towing a trailer 4000# has been pretty much the norm for me. :wink:

Except in the winter

papaindigo · **Posted:** Fri Sep 05, 2014 8:56 am

Tons of variables related to mpg. Simplistic version is maximize the amount of driving in the "highest" gear for the driving conditions without excessive speed running into wind resistance which on the highway translates to ca. 1,800 rpm at a real 62-63mph or so and a GDE EcoTune.

Other factors
1. your driving habits - use of foot on "go" and "stop" pedals
2. weight inside vehicle
3. tires - psi and weight
4. dragging front brakes due to swollen rubber boot
5. wind speed and direction
6. terrain - lower mpg going up vs. higher mpg going down
etc.

No knowledge about lifts

woodtick · **Posted:** Fri Sep 05, 2014 9:01 am

jeepdan wrote:

You wont see any better without a tune from GDE, simple as that.

But, with a GDE Eco tune, stock size tires inflated to 38psi, stock exhaust and brakes that aren't dragging.

27-28mpg for everyday driving, 30-31mpg interstate (under 70mph), 17.5mpg towing a trailer 4000# has been pretty much the norm for me. :wink:

Except in the winter

I can't stress enough the importance of the GDE tune. Both for performance/ mpg and engine longevity. Make sure the brakes aren't dragging. I have found the need to file on the "fingers" of the brake pads to ensure they do not bind, as well as removing the caliper slide pins and throwing away the rubber sleave. Heavy tires will kill mpg as well. Also keep the tach at a max of 2000 rpm. Keep away from heavy lug mud tires too.

Then mpg will improve.

WWDiesel · **Posted:** Fri Sep 05, 2014 9:45 am

I am running a 2 inch lift with Ironman springs, 245x75 all terrains, 2.5 in/out Flowmaster with no cat, Weeks elbow delete kit, no EGR, and a Stage IV Hot Tune by Marco and I get consistently 33 mpg on highway at ~65 mph.
I get in the mid 20s around town driving as long as I drive it conservatively. (Hard to do when you got a little Italian race motor under the hood!) :ROTFL:

Two thoughts: I do not believe lifting had much of an effect on the mileage.
Larger tires does throw the speedometer off by a small amount due to the slight change in final gear ratio. It takes more HP/torque to get taller tires up and rolling and keep them at speed, so you need a performance tune if you plan on running a larger diameter tire. :2cents:

thermorex · **Posted:** Fri Sep 05, 2014 11:08 am

What throws the mpg away is the heavier wheel and the bigger tire (bigger tire=more weight, just as an idea, there are about 15 lbs difference between same tire in those sizes: 265x75x16 vs 245x70x16), that changes the overall gear ratio, exactly what tjkj2002 said. But, if you have a light foot and know your jeep very well, modify the differential gear ratio, the difference would be minimal, unless you do some very extreme lift, with slip yoke eliminator, 35+ inch tires, 6+ inch lift, etc...

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

I get my best economy cruising in 5th gear while keeping it under 60 mph. I drive mostly city/short freeway trips, usually keep it under 2,200 RPM and I average around 22-24 mpg in the summer. On longer highway trips I regularly achieve 31-33 mpg and have achieved as high as 37 mpg.

Rough numbers based on my driving style and vehicle set-up:

GDE FT Eco Tune: (+) 2-3 mpg
Sasquatch Intake Elbow Kit: (+) 1-2 mpg
2.5" Exhaust: (+) 1-2 mpg
OME Lift: (-) 1-2 mpg
245/75-16 Cooper Discoverer AT3: (-) 2-3 mpg

Still a net increase of 1-2 mpg over stock, even with full skids.

mass-hole · **Posted:** Fri Sep 05, 2014 1:59 pm

weeks101 wrote:

I get my best economy cruising in 5th gear while keeping it under 60 mph. I drive mostly city/short freeway trips, usually keep it under 2,200 RPM and I average around 22-24 mpg in the summer. On longer highway trips I regularly achieve 31-33 mpg and have achieved as high as 37 mpg.

Rough numbers based on my driving style and vehicle set-up:

GDE FT Eco Tune: (+) 2-3 mpg
Sasquatch Intake Elbow Kit: (+) 1-2 mpg
2.5" Exhaust: (+) 1-2 mpg
OME Lift: (-) 1-2 mpg
245/75-16 Cooper Discoverer AT3: (-) 2-3 mpg

Still a net increase of 1-2 mpg over stock, even with full skids.

I wonder if the skids help smooth out airflow under the jeep. Kinda like how supercars have completey flat bottoms to reduce drag and increase downforce. I dont know what they look like so im just making things up.

I can get upwards of 30 mpgs with relative ease. Last time I hand calculated I averaged like 28.5 for a tank including both city and highway. Evics said 29 or 29.5 i believe.

-GDE Hot Tune
-AFE Air Filter
-Weeks Elbow
-Muffler Removed
-Stock Tires

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

thanks for all of the advice. the eco tune sounds great but it is expensive. like 700$. if i only gain 3 mpg on average it would take 50k miles to just pay for it ($3.60 diesel). wouldn't be worth the effort for me. please correct me if my math is flawed. i am interested in a WVO conversion. if i do that i would get a tune as well. i have searched the forum for info on WVO with little result. if you know of a good thread or member for this topic let me know.

a couple of you have mentioned brake drag. i had the front drivers wheel jacked off the ground and it didn't spin freely. it didn't take a lot of effort, but i think the brake was engaged very slightly. the PO installed new front brakes shortly before he sold it. the front brakes are producing a lot of brake dust. how can i tell if the drag is normal? should the wheel spin completely free? like not stop the instant i quit turning it?

dirtmover · **Posted:** Fri Sep 05, 2014 3:56 pm

From new my oil was as black as the ace of spades and felt gritty about 500km after an oil change. I performed the ORM, the CEL came on as expected but the oil got just as dirty, just as quick. I was never convinced the ORM actually achieved anything.

Two years ago I upgraded to the GDE ECO tune and now my oil is a dirty golden colour very similar to gasser after 10,000km. It no longer feels gritty. I get a 2mpg improvement in the winter and double this in the summer.

My FCV broke. An adjustment to the tune extinguished the CEL which was required to pass emissions where I live. This saved me around $300 in parts.

The tune paid for itself in the time I've owned it. I wish I hadn't procrastinated and got it when it first came out. I would have been about $400 better off in fuel savings.

Sure it's quite pricey at $700 for the tune and programmer but it doesn't take much to do $700+ worth of damage to this engine.

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

a second engine tune for current flash tool owners is only $100. i could drive a good distance and buy a guy some beer if he were to program my crd for me......anyone interested? i could drive up to 400 miles and it would still save me money.

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

OR you could support the few small businesses dedicated to our rare CRDs.

JieselDeep · **Posted:** Fri Sep 05, 2014 4:30 pm

I believe the tunes are keyed to the vehicle's vin number.

papaindigo · **Posted:** Fri Sep 05, 2014 4:44 pm

The tunes are VIN specific and cannot be uploaded to a second vehicle and, in addition, the flash tool once used to load a tune is also keyed to that vehicles VIN. In the latter case the flash tool can be used to read and clear ECU codes on other vehicles but only works for the purpose of tuning on the vehicle for which the tune was purchased although I think Keith knows how to break the flash tool VIN link if for some reason you want to or have to use the tool to load a separate tune on another CRD as in say for example your CRD gets totaled, like my original 05, and you need to use the flash tool on a replacement CRD, like my replacement one.

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

The website states " second engine tune". They will make 100$ for sending an electronic file. They will not have to buy or build flash tools to resell. I believe my proposal is in the spirit of their second engine price offer. I am not trying to be shady in any way. Just frugal. If I sell the liberty in a year or so I will not have paid for the tune by far. If I can get it done for half or less I have a chance at recouping my investment within a year and I won't feel bad about selling it to finance my next toy. Tunes usually don't increase resale value. If anyone is interested in programming my rig please contact me by private message and I will contact Green diesel to see if it is allowed. If they say no I will not pursue it. But right now I don't know anyone with a programmer so I won't bug them about it

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Optimum speed for mpg and other advice wanted

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