What am I missing - MPG

76Bronco · **Joined:** Thu Nov 06, 2014 9:57 am **Posts:** 18

So here is my story. I bought a 05 Liberty with 113k, previous owner did the timing belt at 95k, GDE Eco Tune, updated fuel head and Samco hoses.

This is what I have done so far
Euro Converter
Fresh Mopar ATF+4
Wix Filter kit
Airtex Lift Pump
Changed T Case Fluid
Changed Diff Fluid - Mobil 1 75w90 (Front and Rear)
Fuel Filter
Weeks Intake
New Intake hose from Air Cleaner to Turbo
New Battery

The Jeep has P245/75R16 Cooper AT3s and the OME 2" lift. So far out of this thing I can only get 20mpg Highway, with the occasional 23 Highway. I usually cruise 65-70 or so. Anyone know what I could do to sneak out a few more MPGs?

Thanks

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

if you have an OBD monitoring tool, measure the MAF at idle and post the flow data. That can be a good indicator of rocker arm wear. Worn rockers reduce valve lift and lead to a drop in fuel economy. GDE

PALiftedKK · **Posted:** Thu Dec 04, 2014 12:08 pm

76Bronco wrote:

So here is my story. I bought a 05 Liberty with 113k, previous owner did the timing belt at 95k, GDE Eco Tune, updated fuel head and Samco hoses.

This is what I have done so far
Euro Converter
Fresh Mopar ATF+4
Wix Filter kit
Airtex Lift Pump
Changed T Case Fluid
Changed Diff Fluid - Mobil 1 75w90 (Front and Rear)
Fuel Filter
Weeks Intake
New Intake hose from Air Cleaner to Turbo
New Battery

The Jeep has P245/75R16 Cooper AT3s and the OME 2" lift. So far out of this thing I can only get 20mpg Highway, with the occasional 23 Highway. I usually cruise 65-70 or so. Anyone know what I could do to sneak out a few more MPGs?

Thanks

seems like you are getting good mileage compared to every one else on this forum. I get around 12 city and 15 highway and off-road, and that's driving like a snail.

the only thing I could think of would be to reset the ecu. not sure if you have an electronic radiator fan but if not install one and that would take of a load on the engine.

clean off the MAF sensor.

you own a jeep, not a Prius!

76Bronco · **Joined:** Thu Nov 06, 2014 9:57 am **Posts:** 18

I did clean the MAP on the engine, but I have not looked at the MAF. What is the other sensor on the airbox? It has a freshly cleaned K&N Filter also. Im not the biggest fan of them, but they were there from the PO. Ill hook up my OBD2 setup and see what data I can post. Thanks.

Nate

thermorex · **Posted:** Thu Dec 04, 2014 1:37 pm

76Bronco wrote:

I did clean the MAP on the engine, but I have not looked at the MAF. What is the other sensor on the airbox? It has a freshly cleaned K&N Filter also. Im not the biggest fan of them, but they were there from the PO. Ill hook up my OBD2 setup and see what data I can post. Thanks.

Nate

Just make sure the engine is warm at operating temperature and at idle. Otherwise the values won't be accurate.

gmctd · **Posted:** Thu Dec 04, 2014 1:53 pm

Are you in hill country or a flatlander?

Road and trail tires lower fuel economy vs street tires due to increased rolling resistance.

Wide tires reduce fuel economy due to increased rolling resistance.

Wide tires reduce fuel economy by projecting past the fender flares into the air stream.

Wider wheels reduce fuel economy by projecting past the fender flares into the air stream.

Any tire\wheel alteration reduces fuel economy due to altered aerodynamic ground-effect.

Large diameter tires reduces fuel economy due to increased loading and increased rolling resistance.

Low tire pressure reduces fuel economy due to increased rolling resistance.

Over-active right foot (my personal nemesis, eh) makes for variable reduced fuel economy.

Winter temps and road conditions reduce fuel economy.

Winter fuels reduce fuel economy.

Winter muff on the front grille reduces fuel economy.

Speeds above 65mph reduce fuel economy normal to 65mph fuel economy.

Carpooling reduces fuel economy.

Carrying lotsa junk in the back reduces fuel economy.

Carrying stuff on the roof rack reduces fuel economy.

Installing those ridiculously-huge multi-winged windshield wipers reduces fuel economy.

Installing those ridiculous (for the street) roof light-bars reduce fuel economy.

Installing off-road lighting -front bumper or\and roof-mount - reduces fuel economy.

Installing off-road bumpers reduces fuel economy.

Lifted\jacked chassis\body reduces fuel economy.

Incorrect replacement disc brake pads can reduce fuel economy.

Incorrect final drivetrain lubricants can reduce fuel economy.

Dirty or incorrect air filter reduces fuel economy.

The mechanical engine fan reduces fuel economy only when additional cooling is required for towing or when using the AC, which reduces fuel economy

Oem centrifugally-clutched thermostatically-controlled hydraulically-coupled engine fan declutches and does not function at hiway speeds due to massive air-flow thru radiator - you can test this function by rotating the fan when engine is cold (should be stiff, not easily rotated), then again just after shut-down when engine is at operating temps (should rotate easily)

Burning the AC in slow traffic will activate the centrifugally-clutched thermostatically-controlled hydraulically-coupled function to drive the fan blades for required cooling necessitated by all air-flow pre-heated after passing thru hot AC condenser, which also activates the auxilliary electric fan directly in front the AC condenser
- alternator is under ECM-control to reduce engine loading, increasing fuel economy - additional electrical loading by this fan, or other additional fans, increases alternator output, increasing engine loading, reducing fuel economy

The centrifugally-clutched thermostatically-controlled hydraulically-coupled fan will be not easily rotated under this hot condition immediately after shut-down, but will free up as temperature drops toward ambient

If the centrifugally-clutched thermostatically-controlled hydraulically-coupled fan-clutch binds up and is always difficult to rotate, replace it with oem factory replacement centrifugally-clutched thermostatically-controlled hydraulically-coupled clutch
- most aftermarket fan-clutches are either centrifugal controlled or thermostatic controlled, but seldom both, and will reduce fuel economy due to functional limitations

Centrifugal and thermostat control both use a calibrated fluid that thickens when heated - the thermostatically-controlled valve version allows more precise control of the hydraulic coupling by allowing the fluid to pass back and forth between the reservoir and the coupling passages as needed to control air-flow volume and coolant temperature

Thermostat-control is evidenced by the bi-metal coil on the shaft in the center of the front clutch face - this coil extends\lengthens when hot, retracts\shortens when cold - the coiled-shape allows rotary motion which turns the shaft, controlling an internal rotary gate-valve
- cold closes the valve, keeping the cool fluid in the reservoir, minimal fan coupling
- hot opens the valve allowing the fluid to flow into the internal passages, increasing hydraulic coupling, maximum fan coupling
- cooling closes the valve, allowing the cooling fluid to pass back into the reservoir, minimizing fan coupling
- initial stiff rotation when cold is resulted when the coupling fluid seeps into the coupling passages when engine is not running and fan is not rotating - rotation when engine is running returns the fluid to the reservoir

I do not recommend removing the engine-driven fan unless proceeding to replace the timing belt or\and associated activity

76Bronco · **Joined:** Thu Nov 06, 2014 9:57 am **Posts:** 18

Mostly flat. I was trying to figure out what the optimal RPM for fuel economy is on these? At 60mph it almost seems like its lugging the engine. 65-70 seems like its in the optimal RPM range. About 2k

gmctd · **Posted:** Thu Dec 04, 2014 3:25 pm

The "lugging" effect is much greater with a 4-cyl than V6 or V8, even greater if Diesel, but is not harmful to the engine - ~ 2k-rpm at hiway speed is normal - established economy-ratings at 65mph will always drop as speed increases due to increased aerodynamic impedance and rolling resistance - road-surface material and condition will also affect economy

Not much way to significantly improve fuel-economy in winter climes

amslube · **Posted:** Thu Dec 04, 2014 3:37 pm

All of the above and one other item, with larger than stock tires there are fewer tire revolutions per mile which translates into less miles racked up on the odometer which when divided by gallons consumed equals less MPGs. My '05 stock tire is a 225 75 16 and my speedometer is right on with GPS.
One thing I would like to add, but but not related to my CRD...I have a '11 Ram 2500 Laramie with the Cummins with 2WD. Just by changing tires from the stock Michelin with a summer thread to Nitto Terra Grapplers with a more aggressive thread, my MPG went down almost 3...same size tire.

76Bronco · **Joined:** Thu Nov 06, 2014 9:57 am **Posts:** 18

I plan on getting some highway tread tires, and then keep the Cooper AT3s for when I go up hunting. Hardcore off road is for the Bronco. I cleaned the MAF and replaced the fuel filter today. Im happy with it, just trying to squeak out as much as I can get.

gmctd · **Posted:** Thu Dec 04, 2014 5:22 pm

Correct, and good input - tire-size does affect calculations in the speedometer, ABS module, ECM, and TCM - modern EFI systems have a programmable entry for correction to new size so the ECM is not dumping fuel where it's not needed

You would think similar-tread larger tires would be like an additional over-drive gear, but doesn't always workout that way due to increased ground-effect, rolling resistance, and drive-train loading from the outer ends of the rear axle, rather than reduced rpm from the transmission to the rear wheels\tires - larger tires can create more mechanical loss

Not even to mention aggressive treads, sipes, and cleats on the road'n'trail tires

76Bronco · **Joined:** Thu Nov 06, 2014 9:57 am **Posts:** 18

Thanks for all the replies. I have been a diesel mechanic for years on heavy equipment, and Ford 7.3s. This Jeep is a new adventure. Im just figuring out all the little quirks about these like all the knowledge I have gained about the Ford 7.3 over the years. Ill get some MAF numbers this week or so and see how those rocker arms are doing.

gmctd · **Posted:** Thu Dec 04, 2014 6:35 pm

76Bronco wrote:

Thanks for all the replies. I have been a diesel mechanic for years on heavy equipment, and Ford 7.3s. This Jeep is a new adventure. Im just figuring out all the little quirks about these like all the knowledge I have gained about the Ford 7.3 over the years. Ill get some MAF numbers this week or so and see how those rocker arms are doing.

Belated welcome to the forum - and, if you have the need to know, L.O.S.T. KJ has the know how and why of it

ArmyChief · **Posted:** Thu Dec 04, 2014 6:43 pm

GreenDieselEngineering wrote:

if you have an OBD monitoring tool, measure the MAF at idle and post the flow data. That can be a good indicator of rocker arm wear. Worn rockers reduce valve lift and lead to a drop in fuel economy. GDE

Kieth,

Do you have a known good at what RPM?

Thanks

thermorex · **Posted:** Thu Dec 04, 2014 6:53 pm

This is what he posted a while ago, for sea level:

17.5g/s is close to the factory 18.2g/s flow number and most likely the rocker arms are still in good shape.
Flow rates below 15 g/s most likely exhibit some degree of rocker wear. Below 13g/s and all the rockers are wasted.

dh100m · **Posted:** Thu Dec 04, 2014 7:28 pm

I get an average hy city of 30mpg imperial gal drive on boost gauge no vicose heater electric
fans they only come when towing in summer hy 65mph most are 20 miles or less

user113 · **Posted:** Thu Dec 04, 2014 10:24 pm

thermorex wrote:

Just make sure the engine is warm at operating temperature and at idle. Otherwise the values won't be accurate.

Reminds me, since you haven't mentioned it previously, have you verified your thermostat is not broken? The needle should be just barely to the left of straight up when fully warmed up. If the engine doesn't get up to temp, your economy will suffer.

I have somewhat big tires (245/75R16), an ARB bumper (about as aerodynamic as the rest of the jeep), and the GDE HOT tune. On my recent thanksgiving road trip with winter fuel I averaged 27.5 mpg (hand calculated) while driving mostly between 65-75 mph, between 1.8K and 2K rpm, from VA to MO and back.

thermorex · **Posted:** Thu Dec 04, 2014 10:33 pm

user113 wrote:

thermorex wrote:

Just make sure the engine is warm at operating temperature and at idle. Otherwise the values won't be accurate.

Reminds me, since you haven't mentioned it previously, have you verified your thermostat is not broken? The needle should be just barely to the left of straight up when fully warmed up. If the engine doesn't get up to temp, your economy will suffer.

I have somewhat big tires (245/75R16), an ARB bumper (about as aerodynamic as the rest of the jeep), and the GDE HOT tune. On my recent thanksgiving road trip with winter fuel I averaged 27.5 mpg (hand calculated) while driving mostly between 65-75 mph, between 1.8K and 2K rpm, from VA to MO and back.

Since you have an arb bumper, would you mind answering a question? How much do you think the arb bumper will affect the front suspension ground clearance, more precisely, hat would be the difference between stock, plastic bumper and arb bumper in suspension "sagging", is it going to drop more than 1/2 inch?

ArmyChief · **Posted:** Thu Dec 04, 2014 11:39 pm

thermorex wrote:

This is what he posted a while ago, for sea level:

17.5g/s is close to the factory 18.2g/s flow number and most likely the rocker arms are still in good shape.
Flow rates below 15 g/s most likely exhibit some degree of rocker wear. Below 13g/s and all the rockers are wasted.

Thanks sir, I'm assuming that's with EGR Closed, as EGR would lower those numbers.

76Bronco · **Joined:** Thu Nov 06, 2014 9:57 am **Posts:** 18

Thermostat is working, nice heat and the needle is just left of center. I forgot my OBD2 stuff this morning, so Ill have to work on that this weekend.

What am I missing - MPG

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