When can we expect better fuel mileage?

[Jeepleap]

When can we expect better fuel mileage? I was disappointed to hear there wasn't much of a step forward when it comes to fuel efficiency in the WK2s.

[Escape]

LOL!

Sorry man had to.

[White Chocolate]

Man, its a Jeep LOL....they have power, they are a very stong pulling vehicle.

if your looking for mpg, buy a hybrid car LOL.

[Steeler]

Sorry to say if you want fuel economy a 5000lbs Jeep shouldn't be your 1st choice. That being said I was impressed that Car and Driver observed 19 mpg on their test of a 3.6 powered Laredo X. Factor in that, in the same issue they tested the new four cylinder Buick Regal and they only averaged 22 mpg.

[Joe in PA]

You are talking about a 2.5 ton brick on wheels! The only real chance at respectable mileage would be a diesel and Jeep has never been able to figure out how to do that in a way that the average Jeep owner would be willing to accept.

[Repo503]

hmmm...I could sell you a tornado, or maybe just some magnets to stick on your fuel line...PM me and I'll send you a PO box # to send your cash to.

[dubwarren]

When can we expect better fuel mileage? I was disappointed to hear there wasn't much of a step forward when it comes to fuel efficiency in the WK2s.


what better could you ask for than 15 city, 18 hwy? Im happy with it anyway.....but then again i have a 5 minute commute with no stops.

[bh22jeep]

I can get 24 on the highway doing 80.

[whatevrworks]

I will hug a tree for you to make you feel better! :D

[Knightrider03m]

After your 1st oil change you should start seeing better gas mileage then what you have. I always change the oil on a new engine at 2K miles.

[dubwarren]

After your 1st oil change you should start seeing better gas mileage then what you have. I always change the oil on a new engine at 2K miles.


im at 2k now. so i guess ill have it changed....

[J13ntv]

Its better when is new to change the oil earlier then usual, just to get out the fine particles and possible tiny metal debris and such from being a new engine that may be in there..

[boarderman23]

I assume when they start using the new 8-speed gas mileage will improve.

[Bmwister]

I assume when they start using the new 8-speed gas mileage will improve.

Sorry to dredge up an old thread, but I doubt the 8spd will do much for economy. I test drove a Q5 with 8spd and it didn't impress me much and it's the same supplier for Jeep (ZF). If anything, I would think it could be annoying to have an 8spd constantly shifting (for minor economy gains) especially in a traction-focused environment. Since the powerbands are quite fat for the Hemi and V6, using an 8spd would only make sense, IMHO, if they made shorter 1-4 gears with "normal" 5-8 gears to give better acceleration from a stop in city driving but preserve hwy cruise; that might help the city mpg rating but do nil for highway mpg where surface area, Cd and weight matter more.

FWIW, I've asked three different WK2 owners (strangers) how their fuel economy was for their vehicle. All were V6 4x4 Laredo versions. One owner said she had no idea but could drive from Chicago to St Louis and back on one tank. The 2nd person said he didn't know and didn't care. The last person I spoke to said he got 15-18mpg (per computer) in the Chicago suburban crawl, and sees 26mpg on the computer for a long interstate trips (but not verified with brim-to-brim fill ups).

[SMG1]

Sorry to dredge up an old thread, but I doubt the 8spd will do much for economy. I test drove a Q5 with 8spd and it didn't impress me much and it's the same supplier for Jeep (ZF). If anything, I would think it could be annoying to have an 8spd constantly shifting (for minor economy gains) especially in a traction-focused environment. Since the powerbands are quite fat for the Hemi and V6, using an 8spd would only make sense, IMHO, if they made shorter 1-4 gears with "normal" 5-8 gears to give better acceleration from a stop in city driving but preserve hwy cruise; that might help the city mpg rating but do nil for highway mpg where surface area, Cd and weight matter more.

FWIW, I've asked three different WK2 owners (strangers) how their fuel economy was for their vehicle. All were V6 4x4 Laredo versions. One owner said she had no idea but could drive from Chicago to St Louis and back on one tank. The 2nd person said he didn't know and didn't care. The last person I spoke to said he got 15-18mpg (per computer) in the Chicago suburban crawl, and sees 26mpg on the computer for a long interstate trips (but not verified with brim-to-brim fill ups).

Surface area, Cd and weight certainly have a more significant impact on highway mpg, but you can't discount the fact that an 8-speed will lower the highway rpms and subsequently improve fuel economy. Most manufacturers have pretty much proven that the 6, 7 and 8-speed transmissions far outshine their 5, and dare I say 4, speed counterparts in terms of size, weight and mpg.

[OneCent]

well, maybe this time you have luck for the new VM Diesel (around 240PS and 550nm / 405lb tork) in the US. With that engine mpg could be between 19-28mpg.

[Bmwister]

Surface area, Cd and weight certainly have a more significant impact on highway mpg, but you can't discount the fact that an 8-speed will lower the highway rpms and subsequently improve fuel economy.

That's too simple a statement; I hear this all the time, but reducing rpm to get better economy is only partly true if the engine can produce the required horsepower efficiently and harmlessly at that lower rpm to maintain desired cruising speed.

Ignoring acceleration: Regardless of rpm, a vehicle requires specific horsepower to maintain speed on a level road (let's just say it's 30hp@60mph for the JGC, for example)...the surface area, Cd, weight (for hill climbs) determine the horsepower needed. Add in wind and hills and the power required to maintain cruise speed goes up substantially.

You can run the engine at 6000rpm with a small throttle opening to get that 30hp or you can lug the engine at 1000rpm to get the 30hp and maintain cruising speed. Simply revving the engine at 6 times the rpm doesn't equate linearly with using 6 times the fuel, but it does have an affect...

The higher engine speed affects fuel economy from the frictional losses at the high rpm and leads to excessive engine wear. However, if you lower the engine rpm too much, not only can the engine lug inefficiently, but the low rpm may not enable sufficient oil circulation or coolant flow which could lead to engine overheating, excessive wear and early engine failure. (Idling is a minimal load condition so idling doesn't count as dangerously low rpm)

There is a median range that balances efficient engine rpm with horsepower requirements for cruising. Too high an rpm isn't good, and too low an rpm isn't good; maybe worse. It's just not simply "lowering the rpms" to get better economy, it's lowering the required power needed to accelerate and cruise; better lubricant in the engine, trans and drivetrain are also fuel economy factors among those mentioned.

Sorry to be long winded, but I've built many engines over the years and there is no changing the laws of physics.

[DavidB]

20 MPG Hemi compared to 14MPG in an Escalade...Im a Happy Camper

[AIR_RAM]

I have found that first of all... anything with 30" tall tires and a .67 overdrive should have 4.56's as the primary gear ratio.

RPMS alone do NOT dictate fuel economey... as mentioned above its the load on the engine at any given RPM that has more of an effect on fuel economey then RPMs alone.

With that said... Light foot syndrom can hurt your fuel economey... WHY? Because it will take you 2 miles under a constant load which will hurt your MPG.

TRICK #1

From a stop, Pull out and bring your RPMS to 2000. On shift bring it back to 2000RPMs... and do the same for each shift... untill you reach your desired speed.


TRCIK #2
Only after I have reached my desired speed using the above 2000 RPM trick I use my instant MPG readout when I accelerate. I do so in a way that my MPG stay above my current high... If I give too much throttle my MPG indicator drops like a rock and goes below my current high... but if I baby the gas I can keep the actual MPG above my current high... T Once you hit 40-45MPH let off and lightly use the throttle to bring you up to speed.

TRICK #3
COAST COAST COAST... when ever possible... Dont let your engine drag your speed down... toss it into nutral and coast to the next stop. If you know you have a stop 400-500 yards a head of you and you know you will need to use your brakes... then toss it into nutral and coast. There are a few streets where I can coast for over 1/4 mile and barely lose any speed at all before I appy the brakes to stop at the stop sign.

Other then normal maintainance like air pressure and lubircants.... Driving habbits can play a big role in your MPG.

Correcting the gear ratios will help eliminate wasted fuel on acceleration and get us into our overdrives sooner... at the same time they will offer more mechanical advantage in order to HOLD those super high ratios more effectively & effeciently.



SPEED SAFE, NICK

[ryorde]

Its pretty simple physics really. You can’t have horsepower and good fuel economy. It’s just not possible. There is a direct relationship between horsepower and fuel burned. The mass of the vehicle, friction, and air resistance will dictate how much horsepower is required to accelerate the vehicle to a given velocity (speed and direction).

Of course harder acceleration requires more horsepower, and therefore decreased fuel economy. Likewise, you will see better gas mileage on a highway where a constant speed is maintained for a long period of time, with not much acceleration required. Although the faster you drive on the highway, the more friction you create between your car and the air/road and consequently more horsepower is required to maintain speed, hence the usual decrease in MPG once you exceed 70 MpH or so. In City situations where lots of stopping and starting are more frequent, gas mileage suffers as a result of more frequent acceleration and less time spent traveling at a constant speed.

No matter how you look at it, a given amount of power (for example 200 horsepower) will always be required to accelerate, in this case a 5000 pound Jeep, from 0 miles per hour to 60 miles per hour in a given time frame. This is why there isn’t a significant (Emphasis on “significant”) difference between the estimated EPA fuel economies of the V6 versus the V8. Despite the difference in engine size, both will have to output 200 horsepower for example (not an actual figure, just using it for the sake of the analogy) to accelerate from 0-60. That 200 horsepower will require so many cubic centimeters of fuel to be burned to generate so many joules of energy that the mechanics of the engine can transfer to the wheels.

Albeit some engines are not as efficient as others, most built in this age are about as good as its going to get. With the introduction of engine control computers, fuel injection, and a myriad of other sensors and controls, engineers have been able to ensure that as much of the energy generated by burning fuel is transferred to the wheels as possible with as little energy lost to friction and heat as possible.

As the engine gets larger, the potential for energy grows, but in turn the amount of energy required to combat the added friction of the extra parts and simply keep the engine running grows as well. This is one of the few real reasons you will see a smaller engine get better mileage. This also applies to two wheel drive versus four wheel drive. More metal takes more energy to move, more energy requires more fuel it is as simple as that.

[ryorde]

I have found that first of all... anything with 30" tall tires and a .67 overdrive should have 4.56's as the primary gear ratio.

RPMS alone do NOT dictate fuel economey... as mentioned above its the load on the engine at any given RPM that has more of an effect on fuel economey then RPMs alone.

With that said... Light foot syndrom can hurt your fuel economey... WHY? Because it will take you 2 miles under a constant load which will hurt your MPG.

TRICK #1

From a stop, Pull out and bring your RPMS to 2000. On shift bring it back to 2000RPMs... and do the same for each shift... untill you reach your desired speed.


TRCIK #2
Only after I have reached my desired speed using the above 2000 RPM trick I use my instant MPG readout when I accelerate. I do so in a way that my MPG stay above my current high... If I give too much throttle my MPG indicator drops like a rock and goes below my current high... but if I baby the gas I can keep the actual MPG above my current high... T Once you hit 40-45MPH let off and lightly use the throttle to bring you up to speed.

TRICK #3
COAST COAST COAST... when ever possible... Dont let your engine drag your speed down... toss it into nutral and coast to the next stop. If you know you have a stop 400-500 yards a head of you and you know you will need to use your brakes... then toss it into nutral and coast. There are a few streets where I can coast for over 1/4 mile and barely lose any speed at all before I appy the brakes to stop at the stop sign.

Other then normal maintainance like air pressure and lubircants.... Driving habbits can play a big role in your MPG.

Correcting the gear ratios will help eliminate wasted fuel on acceleration and get us into our overdrives sooner... at the same time they will offer more mechanical advantage in order to HOLD those super high ratios more effectively & effeciently.



SPEED SAFE, NICK

You might consider that some (not all) engines of newer design actually cut fuel to the engine entirely at high speed when you release the accelerator and use the friction from the wheels turning the transmission to keep the engine turning. Then the engine is instantly reignited without the use of the starter when you press the accelerator again. However when you shift into neutral as trick number 3 suggests, the computer cannot cut fuel to the engine because the transmission is no longer turning the crankshaft to keep the engine turning and the starter would be required to reignite the engine, which would cause a lot of wear and could not be done as quickly or seamlessly. As a result you end up burning more fuel not less when you shift into neutral. Most people don’t even notice when ECUs do this.

[jeep2011]

With that said... Light foot syndrom can hurt your fuel economey... WHY? Because it will take you 2 miles under a constant load which will hurt your MPG.

TRICK #1

From a stop, Pull out and bring your RPMS to 2000. On shift bring it back to 2000RPMs... and do the same for each shift... untill you reach your desired speed.

TRICK #3
COAST COAST COAST... when ever possible... Dont let your engine drag your speed down... toss it into nutral and coast to the next stop. If you know you have a stop 400-500 yards a head of you and you know you will need to use your brakes... then toss it into nutral and coast. There are a few streets where I can coast for over 1/4 mile and barely lose any speed at all before I appy the brakes to stop at the stop sign.


AHHHH 2000 RPM's? The above statement cancels that out. I don't think it is possible to accelerate any slower than 2000 RPMS, LOL

Also the neutral statement is false nowadays. You are actually burning more fuel by putting the transmission in neutral. Most cars today when you take your foot off the gas and you are coasting the fuel supply to the engine is shut off giving you nothing but the BEST mileage. When you shift into neutral your engine is using the fuel to keep itself running. In turn you are getting the worst mileage possible considering the alternative.

[ryorde]

AHHHH 2000 RPM's? The above statement cancels that out. I don't think it is possible to accelerate any slower than 2000 RPMS, LOL

Also the neutral statement is false nowadays. You are actually burning more fuel by putting the transmission in neutral. Most cars today when you take your foot off the gas and you are coasting the fuel supply to the engine is shut off giving you nothing but the BEST mileage. When you shift into neutral your engine is using the fuel to keep itself running. In turn you are getting the worst mileage possible considering the alternative.


LOL. Same comment 2 minutes apart.

[moosehead]

i'm diggin your avatar ryorde. it's also a good analogy for power superceding mpg.

[AIR_RAM]

Im not new to MDS or cylinder deactivation methods... I do understand how they work and how in most cases they improve MPG over traditional engines. But I also understand that the drag of 8 cylinders in gear consumes energy.

Try it... you may find that by putting it into nutrual therefor removing the DRAG from your engine while you coast uses LESS fuel. This is not an opinion... We currently are getting over 18MPG city when we apply this driving habbit... It works, and is worth about 2MPG.

Its all good, coasting works well for us... If you find yourself board and willing to try somthing new... give it a shot. You may be pleasently surprised at your MPG gains.

NICK

[Milous]

...You may be pleasently surprised at your MPG gains...
And perhaps unpleasantly surprised when you have transmission/drivetrain issues. NOT a good idea.

[jeep2011]

And perhaps unpleasantly surprised when you have transmission/drivetrain issues. NOT a good idea.

+1 for that. Plus you'll be replacing brakes sooner. I am pleased with the mileage I get with the hemi, even with my lead foot.

[ryorde]

Im not new to MDS or cylinder deactivation methods... I do understand how they work and how in most cases they improve MPG over traditional engines. But I also understand that the drag of 8 cylinders in gear consumes energy.....

NICK

I dont think you understand how this system works. Yes 8 cylinders in gear adds drag, but when you are coasting while in gear the computer shuts the fuel injectors OFF. NO energy is wasted because NO fuel is getting burned. The drag is what keeps the engine going without gasoline. If you shift into neutral you force the engine to continue burning gasoline to keep the engine going. Coasting in neutral is a bad idea anyway, not to mention illegal in some if not all states. (I live in VA where it is illegal, I dont know about other states.)

[2011JGC]

Sent from my DROIDX using Tapatalk

[bpmcgee]

Try it...It works, and is worth about 2MPG.

You're saying that simply coasting to stop lights while city driving is saving you 2 MPG?

Just to be extra clear --you state that coasting up to stop lights is giving you a fuel mileage improvement greater than 10%??

Wow. Just wow.

B

Edit: As an afterthought, I'd like to hear how you correlate this with the fact that engines idle at higher rpms in neutral than in gear (with an automatic transmission), and that while decelerating, an engine in gear is unloaded.

[AIR_RAM]

LOL... This is a feebe guys... It works just as I have posted.. and I have not had any issues with it. So until you try it, all your offering is a personal opinion based on an opinion...

Since I have tested the theory and have been practicing it doing so for several tanks of fuel... Im one up on you with a notch towards the "PERSONAL EXPERIENCE" over your "PERSONAL OPINION".... Take it for what its worth... Just trying to offer some good sound advice on increasing fuel economey that works... your not going to win any debates when your case is built on your own personal OPINION.

In the end it really does not matter to me if you do it or not... So far I have offered some advice to increase fuel economey... what have each of you offered as far as advice goes other then attempt to discredit what I have already found to work well?

It is what is... And I stand by what I have posted as a way to increase your fuel economey with your JEEP.

SPEED SAFE, NICK

[AIR_RAM]

I dont think you understand how this system works. Yes 8 cylinders in gear adds drag, but when you are coasting while in gear the computer shuts the fuel injectors OFF. NO energy is wasted because NO fuel is getting burned. The drag is what keeps the engine going without gasoline. If you shift into neutral you force the engine to continue burning gasoline to keep the engine going. Coasting in neutral is a bad idea anyway, not to mention illegal in some if not all states. (I live in VA where it is illegal, I dont know about other states.)

Really... so the engine shuts off the fuel injectors completley off when in gear... So please tell me, if the engine is not running on fuel... how does it stay on? I would think it would need fuel to stay running... at least in my 25+years working on engines and racing... I never heard of an engine that does not need fuel to stay running.

I beleive you have been misinformed or just dont understand how MDS works. I think what you had meant to suggest is that when not under load the engine goes into MDS and only runs on 4 cylinders... But it never shuts down all cylinders...This is only because Its only capable of shutting down 4 of the 8 cylinders.

Perhaps you may want to go study up on the MDS system before making another post attempting to discredit my advice. Im not the one trying to make you look bad... Your apparantly after me... So please if you would like to debate... get informed first.

You're saying that simply coasting to stop lights while city driving is saving you 2 MPG?

Just to be extra clear --you state that coasting up to stop lights is giving you a fuel mileage improvement greater than 10%??

Wow. Just wow.

B

Edit: As an afterthought, I'd like to hear how you correlate this with the fact that engines idle at higher rpms in neutral than in gear (with an automatic transmission), and that while decelerating, an engine in gear is unloaded.

Yes... But Im not just coasting mearly 10 feet at a time either... When I see a light turn Yellow and I know I will have to stop I let off the gas and put it into Nutrual... and coast to the stop... The further I can coast the better. Its like driving for free... and the distance you can cover just coasting with no load VS in drive with load is nearly 4 times as far.

RPMS ALONE DO NOT DICTATE FUEL ECONOMEY! Also, rolling in gear will ALLWAYS use more fuel then idle alone.... And there is no way fuel can be cut off 100% if it did the engine would shut off. When coasting in gear your RPMs are higher then when in idle alone. The high idle is more so to the timing advance in idle then it is to do with increased fuel. I can raise and lower my idle on my truck just by adding timing advance... The AFR leans out and in most cases I would add fuel to richen it back up.


SPEED SAFE, NICK

[bpmcgee]

So far I have offered some advice to increase fuel economey... what have each of you offered ...?


Critical thinking.

[AIR_RAM]

Critical thinking.

LOL...

I understand your reserves to the idea... but it works. :thumbsup:

SPEED SAFE, NICK

[ryorde]

AirRam,

You are not listening. This is not a function of MDS. As long as the car is in gear and the wheels are turning, the output side of the transmission is turning. That in turn, drives the torque converter which is connected to the crankshaft. As long as the crankshaft is turning, no other energy is required to keep the engine going. You don’t need a gasoline explosion in a cylinder to drive the piston down if the crankshaft is going to pull it down. Inertia alone is providing all the energy required to move the vehicle forward. By keeping the transmission in gear you allow the wheels to transfer that energy into the engine to turn the crankshaft instead of using the energy generated by gasoline to drive the crankshaft. The same principal applies to MDS however. When it shuts off four of the cylinders do you think it disconnects the pistons from the crankshaft??? No the pistons in those cylinders continue to move up and down just as before, simply without gasoline or a spark. So, when coasting, the computer simply turns all of the spark plugs and fuel injectors off, and the rest of the engine continues to move and function just as before. It is simply getting the energy it requires from another source. This is not a complicated concept to understand.

And just to clarify, I don’t “have it out for you”. A forum is meant to be a place to share information. I don’t think you understand what it is I am trying to say. Miscomunication happens frequently through text, and apparently I have left information out of my previous posts that would have helped you to understand what information I was trying to relay. I apologize for any of my previous posts reading in an offensive manor, as that was not my intent.

[Sparro]

From what I've heard, I believe we can expect a 25% increase in fuel economy when the ZF 8-Speed makes its debut next summer.

[OneCent]

Really... so the engine shuts off the fuel injectors completley off when in gear... So please tell me, if the engine is not running on fuel... how does it stay on? I would think it would need fuel to stay running... at least in my 25+years working on engines and racing... I never heard of an engine that does not need fuel to stay running.


Well, thats not necessary in all situations. When you drive down a hill, and do use your motorbreak (give no throttle), modern engines don't use any fuel. In the past they did, because of cooling. The engine get the rpms from the "powertrain".

[Milous]

... So far I have offered some advice to increase fuel economey...
1. What you are offering is BAD advice... you are NOT gaining ANY increase in MPG whatsoever. Zip, ZERO, 0.0000. You're actually wasting gas by putting your car into neutral!!

As has already been pointed out in this thread, when coasting in gear fuel consumption is at or near ZERO as there is no fuel being injected. When coasting in neutral, the engine is idling and consuming fuel.


2. In addition to wasting fuel, you run the risk of transmission damage...

From the 2011 owners manual:

"...coasting, or driving for any other reason with the shift lever in NEUTRAL can result in severe transmission damage..."

READ the section on recreational towing to understand more about reasons to not have the transmission in neutral when the vehicle is moving.


3. I won't get into all of the UNSAFE reasons why drivers should NEVER put their vehicle in neutral when driving, anyone who does not understood the risks should have their license revoked and invest in a bicycle.


BTW, if you are using the EVIC to calculate your supposed fuel gain you might want to know that the calculations used are NOT based on how much fuel is actually consumed.

And you cannot simply divide your actual gallons consumed by your mileage to try and measure supposed savings from coasting. Too many variables. The only accurate way would be with instruments and trained techs. And that has already been done, with the results confirming what has been stated above.

[AIR_RAM]

LOL... there you have it!

It does work!

Coasting has not caused any damage to my 45RFE trans in over 9 very abusive YEARS. BUT if somone where to overshift it past Nutral into Reverse then I can see how damage could happen... The 545RFE is mechanically the exact same transmission in every way except programming. There is no saftety stop on the shifter, this is where the possiblitly for damage could occur. BUT its also all electronic controlled, even the actual shifts are electrical commanded... so I dont even think a missed shift would cause any problems... but I still dont suggest missing a shift.

Pen and paper math must be wrong as well...

I do agree that there are many more veriables involved... and someone is missing a few in their very wrong OPINION.

I see nothing gained by going back and forth... You have your opinions and I have my facts... Lets just leave it at that. Until one of you actually trys it... your opinion will never expand into experience.

Hope you all have a great Thursday....

NICK

[Milous]

...You have your facts and I have my opinions...
Fixed it for ya.

[JoeSchmoe007]

LOL Milo is not messing around :D