Crappy fuel economy?

DieselJeepLuvr · **Posted:** Mon Aug 07, 2017 5:56 pm

My recently purchased libby has 145K and I just can't get the fuel economy I did with my old one. when I bought it I was getting 19-20 mpg on the highway now I'm getting 25-26 but that's with a new transmission, FT Eco-tune, Weeks stage 1 & 2 EGR delete (including cleaning out the intake as best as possible, EHM and a new air filter. It appears that the turbo to intercooler hose has been updated also. My old one just had the EHM & ORM and it got 30-32 mpg and 24 mpg towing my boat.

Any things I should be looking at?

flash7210 · **Posted:** Mon Aug 07, 2017 6:06 pm

25-26 is pretty good.
That's what mine has averaged over the last 10 years.

GordnadoCRD · **Posted:** Mon Aug 07, 2017 6:13 pm

Tires
Air pressure
Suspension
Weight
Dragging Brakes
Differential lube, and condition.
And the big unknown - engine - drivetrain condition from past unknown use.

Locked KJ · **Posted:** Mon Aug 07, 2017 7:10 pm

X2

Just replaced a dragging front left caliper and went from 19 to 21 around town. Stock tune.

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

Check your engine temperature with an OBDII reader. Get an actual measurement and do not go by the O.E. temperature gauge.

CRD owners who claim that it is "ALL GOOD", when the temperature gauge needle is pointed vertically are not correct. When vertical, the actual engine temperature can be as low as 170 degrees, (way too low), or up to 203 degrees, (correct temperature).

Engine temperature has a direct bearing on fuel economy. Too low an engine temperature, and you are wasting fuel because the engine is not running efficiently.

GordnadoCRD · **Posted:** Mon Aug 07, 2017 9:02 pm

That's true also, even if your engine temperature gauge IS correctly calibrated and the thermostat IS working correctly (we're getting into lightening-strike probability here) the 176F temperature is not prescribed and installed with fuel/engine efficiency in mind.

flash7210 · **Posted:** Mon Aug 07, 2017 9:42 pm

GordnadoCRD wrote:

That's true also, even if your engine temperature gauge IS correctly calibrated and the thermostat IS working correctly (we're getting into lightening-strike probability here) the 176F temperature is not prescribed and installed with fuel/engine efficiency in mind.

But yet, his previous CRD got 30 mpg, presumably with a factory thermostat.
Hmmm...

GordnadoCRD · **Posted:** Mon Aug 07, 2017 10:23 pm

flash7210 wrote:

GordnadoCRD wrote:

That's true also, even if your engine temperature gauge IS correctly calibrated and the thermostat IS working correctly (we're getting into lightening-strike probability here) the 176F temperature is not prescribed and installed with fuel/engine efficiency in mind.

But yet, his previous CRD got 30 mpg, presumably with a factory thermostat.
Hmmm...

Quite possibly.
It is only one factor of the equation, after all.

DieselJeepLuvr · **Posted:** Mon Aug 07, 2017 10:29 pm

GordnadoCRD wrote:

Tires Stock sized Toyo AT's
Air pressure 35 psi cold, 38 hot
Suspension Stock
Weight About 175 but not sure how that affects fuel economy :5SHOTS:

Dragging Brakes 35 mile freeway drive in 102 degree weather and I can touch the calipers...
Differential lube, and condition. Service about 38 K ago
And the big unknown - engine - drivetrain condition from past unknown use.

Carfax shows regular maintenance at same dealership most it's life but this is anybodies guess. It did appear to be well taken care of though

Checked the thermostat housing temp after my "test drive" and my pyrometer says 205 degrees F and the thermostat shows a touch before 12:00 and rock steady.

Honestly I've already considered all these. I guess my next step is to put new CAC hoses on just for ships and giggles. Maybe I'm being too anal but because I'm comparing to my last one and maybe it was a "freak of nature" or something...

GordnadoCRD · **Posted:** Mon Aug 07, 2017 10:48 pm

DieselJeepLuvr wrote:

GordnadoCRD wrote:

Tires Stock sized Toyo AT's
Air pressure 35 psi cold, 38 hot
Suspension Stock
Weight About 175 but not sure how that affects fuel economy :5SHOTS:

Dragging Brakes 35 mile freeway drive in 102 degree weather and I can touch the calipers...
Differential lube, and condition. Service about 38 K ago
And the big unknown - engine - drivetrain condition from past unknown use.

Carfax shows regular maintenance at same dealership most it's life but this is anybodies guess. It did appear to be well taken care of though

Checked the thermostat housing temp after my "test drive" and my pyrometer says 205 degrees F and the thermostat shows a touch before 12:00 and rock steady.

Honestly I've already considered all these. I guess my next step is to put new CAC hoses on just for ships and giggles. Maybe I'm being too anal but because I'm comparing to my last one and maybe it was a "freak of nature" or something...

I"m fairly certain you know I meant weight of the vehicle

Unless you're like my dad, who walked to school and back
Uphill and against the wind
Both ways
But that was in Troutdale.

I'm really not sure where to look next.

Turbo vanes not moving freely?
Eroded turbine or compressor wheel blades?
Plugged exhaust catalyst?
Still running factory exhaust?

Mine is a bit crazy when it comes to mileage. By it's self, unloaded, it gets 29-30 consistently and repeatedly. I pulled a 2200lb utility trailer 65-70 mph, and the rig packed full of crap, for 740 miles over a mountain pass, and got a total average of 33.4. Measured and calculated, not EVIC. (it's a little optimistic).
It's got to be aerodynamics somehow. I can't figure it any other way.

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

Quote from DieselJeepLuvr:

"Checked the thermostat housing temp after my "test drive" and my pyrometer says 205 degrees F and the thermostat shows a touch before 12:00 and rock steady."

"Pyrometer"? You mean a temperature gun that measures using a laser? In some circumstances they are not accurate -- just a possibility. How good is your temp gun, if that is what you mean by "pyrometer"?

Here is something else to consider... your O.E. temperature sending unit threaded into your O.E. thermostat may be malfunctioning and sending inaccurate signals to your engine's computer. This condition may cause the computer to tell the fuel system to burn more fuel.

Check the thermostat reading with your gun, and compare the readings with another gun that is known to be accurate if you are not certain of yours is. Check both readings against the OBDII reader reading that takes measurements from the signals sent from the O.E. temperature sending unit to the computer.

To be really accurate, try to aim the temperature guns at the main body of the thermostat housing, not the cap. Or better yet, a spot on the cylinder head, (not the valve cover). If you can hit the cylinder head right where the thermostat mounts to it, that is the ideal location.

WolverineFW · **Posted:** Tue Aug 08, 2017 12:35 am

flash7210 wrote:

GordnadoCRD wrote:

That's true also, even if your engine temperature gauge IS correctly calibrated and the thermostat IS working correctly (we're getting into lightening-strike probability here) the 176F temperature is not prescribed and installed with fuel/engine efficiency in mind.

But yet, his previous CRD got 30 mpg, presumably with a factory thermostat.
Hmmm...

I have in the past achieved 31 US MPG on my CRD, hand calculated, stock tires, no lift on long drives at a steady 60 mph with the stock thermostat.

Sent from my SM-N910W8 using Tapatalk

GordnadoCRD · **Posted:** Tue Aug 08, 2017 1:40 am

Pretty much matches mine.
Tires are a bit wider than stock
No lift
and there is no place around here that steady 60 can be maintained for more than a couple miles.
Still gets a reliable hand-calculated 30 average.

WWDiesel · **Posted:** Tue Aug 08, 2017 10:22 am

I have been able to squeeze 33 mpg, hand calculated, out of mine on interstate steady driving with hills. 245/75 tires with 2.5 lift and Stage IV hot tune. :BANANA:

Tire pressure @ 40 psig
I do believe it could do even better on some real flat land driving like maybe in west Texas or some where similar where there are no hills... :roll:

DieselJeepLuvr · **Posted:** Tue Aug 08, 2017 6:43 pm

TURBO-DIESEL-FREAK wrote:

"Pyrometer"? You mean a temperature gun that measures using a laser? In some circumstances they are not accurate -- just a possibility. How good is your temp gun, if that is what you mean by "pyrometer"?

Yes my "Pyrometer" is very accurate. It reads 212F on boiling water. This isn't my first rodeo

GordnadoCRD wrote:

:ROTFL: I"m fairly certain you know I meant weight of the vehicle

Yes I knew what you meant. Other than an extra pair of work boots and a carter lift pump it's weight is stock weight

I'm really not sure where to look next.

GordnadoCRD wrote:

Turbo vanes not moving freely? Good idea! I will check!
Eroded turbine or compressor wheel blades? I guess I should hook up a boost gauge. Chunks of EGR soot could have caused this. Great thinking!
Plugged exhaust catalyst? Another great idea! Don't know how long they are supposed to last on these rigs???
Still running factory exhaust? Unfortunately Yes

WWDiesel · **Posted:** Tue Aug 08, 2017 9:19 pm

I agree, it could be a partly stopped up CAT
or
EGR valve not fully closing and allowing boost to leak backwards through it thereby loosing boost.
A boost gauge is a good idea to diagnose problem... :wink:

DieselJeepLuvr · **Posted:** Tue Aug 08, 2017 9:45 pm

I did the Weeks stage 1 & 2 so no EGR.

GordnadoCRD · **Posted:** Tue Aug 08, 2017 10:50 pm

The Cats are supposed to be warranted for 100K, but many require replacement before then.
Also, I doubt that the Cat mfrs were counting on all the EGR goop that Didn't get stuck in the intake junction, and made it through to coat the Cat. honeycomb. You could always rod it out, but unless it's licensed in Multnomah county, you shouldn't have to worry about inspections in it's life.
No reason not to wake it up. From another thread:
Best Flow = Straight pipe Get rid of the restrictive Cat and OEM Muffler
Best Scavenging = terminate it in the low pressure area behind the rear wheel.
Best internal sound = terminate it just past the outer body / bumper line behind the rt rear tire, so there is no reverberation.
I chose not to wake the neighbors, and put Flowmaster 942550 tucked up just behind the rear cross member.

Crappy fuel economy?

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