Garbage freeway fuel econ

PCT · Jul 30, 2017

Past few months I have noticed my mpg in the trash! Cruise control set at 70 on flat ground I'm getting 11-13, where I used to get 14-17. Engine seems to struggle to stay to speed while in 6th. Truck seems to produce power alright when giving it throttle, no hesitation not worried about not making a merge or what ever on free way, it's just when crusing. Truck does fine in city, and idles very very smooth.

According to evic i am at 203 coolant temp while on highway. (Oil reads -43) for some reason the 4.7 doesn't report oil temp. Trans temp at 153.

Ambient has been 80-105

I have used half a can of seafoam through intake (spray version). Cleaned air filter, put oem air hat back on, put a full can of seafoam in gas tank. Upper set of plugs have been done 10k miles ago, all fluids on drive line have been flushed or changed. I take great care of my vehicles so almost everything required has been done. I do see a lot of oil mist in the intake manifold, but catch can will fail can smog.... Few things I think are causing, the oil soaked manifold, or when I was loosing my job I used only Safeway gas for about 4 months straight, so maybe the injectors are dirty... Some have mentioned pcv being plugged, and egr being plugged. Gotta pull the pcv valve and clean it, just don't wanna break anything pulling it off. If anyone could steer me in the right direction.

Sent from my SAMSUNG-SM-G935A using Tapatalk

huntergreen · Jul 31, 2017

Is the tc locking when cruising? Have you checked you brakes and callipers ?

bassheadhemi · Jul 31, 2017

If the ecu doesn't see the oil temp it might be thrown off and dump more fuel than it should?

Sent from my SM-N920W8 using Tapatalk

PCT · Jul 31, 2017

huntergreen said:
Is the tc locking when cruising? Have you checked you brakes and callipers ?

Tc= transfer case?

No what should I look for?

Sent from my SAMSUNG-SM-G935A using Tapatalk

PCT · Jul 31, 2017

bassheadhemi said:
If the ecu doesn't see the oil temp it might be thrown off and dump more fuel than it should?

Sent from my SM-N920W8 using Tapatalk

IDK if the ecu isn't detecting or not, I would think it would through a CEL. But on the evic and on my headunit (idatalink OE gauge page) read null. Evic will defualt to coolant temp once coolant is above 100*. scan gauge and headunit will read the null number of -43.

Sent from my SAMSUNG-SM-G935A using Tapatalk

PCT · Jul 31, 2017

This was my my commute to work today, which is mixed flat and 2 hills

Sent from my SAMSUNG-SM-G935A using Tapatalk

reek · Jul 31, 2017

PCT said:
Tc= transfer case?

No what should I look for?

Sent from my SAMSUNG-SM-G935A using Tapatalk

I think he meant torque converter.

PCT · Jul 31, 2017

reek said:
I think he meant torque converter.

I have no idea, how would I know, and what do I want to happen?

Sent from my SAMSUNG-SM-G935A using Tapatalk

Firebird · Jul 31, 2017

Here in N Florida, our fuel the last 2 months has been crap! Everyone I speak to is down on fuel economy and a number of them are reporting drivability issues too. Doesn't matter what make of vehicle or motorcycle, many of us here have noticed the change.

MarshRam · Jul 31, 2017

Firebird said:
Here in N Florida, our fuel the last 2 months has been crap! Everyone I speak to is down on fuel economy and a number of them are reporting drivability issues too. Doesn't matter what make of vehicle or motorcycle, many of us here have noticed the change.

I 2nd that, could be crappy fuel. I'm getting the same mpg as last summer. However, I put in a tuner, exhaust and CAI a couple months ago and gained 1mpg, so definitely not getting the mpg I was last year under the same weather conditions.

PCT · Jul 31, 2017

Firebird said:
Here in N Florida, our fuel the last 2 months has been crap! Everyone I speak to is down on fuel economy and a number of them are reporting drivability issues too. Doesn't matter what make of vehicle or motorcycle, many of us here have noticed the change.

But then I should be noticing this crap fuel economy in my dart, and the dart is dead on what the EPA rates it at. I'm getting 28-29 mixed.

I guess I could run quality gas for the next few tanks see if anything improves. Also going to plug in my scan gauge and have it also read out fuel economy to see if evic is close or if there is something wrong with the calculation.

I'm intrigued to know what could be up with torque converter... I figured if the intake manifold was to blame(because oil build up), the truck wouldn't be running good period.

Sent from my SAMSUNG-SM-G935A using Tapatalk

dan1911 · Jul 31, 2017

PCT said:
But then I should be noticing this crap fuel economy in my dart, and the dart is dead on what the EPA rates it at. I'm getting 28-29 mixed.

I guess I could run quality gas for the next few tanks see if anything improves. Also going to plug in my scan gauge and have it also read out fuel economy to see if evic is close or if there is something wrong with the calculation.

I'm intrigued to know what could be up with torque converter... I figured if the intake manifold was to blame(because oil build up), the truck wouldn't be running good period.

Sent from my SAMSUNG-SM-G935A using Tapatalk

I believe your scan tool and evic will read the same since its getting the same info from the computer. You would be better off doing a hand calculation to get the most accurate gas mileage. I made a simple google sheets (excel) that i can access offline on my phone that I just put the date, odometer, price/gal and it gives me a whole bunch of nerdy info. My evic says I get 15.1 on highway but hand-calced showed an adjusted 17.8 but this is in part to my larger tires and un-adjusted speedometer (I have the conversion in the equation to adjust for large tire size for summer and revert back to stock equation for winter tires)

PCT · Jul 31, 2017

dan1911 said:
I believe your scan tool and evic will read the same since its getting the same info from the computer. You would be better off doing a hand calculation to get the most accurate gas mileage. I made a simple google sheets (excel) that i can access offline on my phone that I just put the date, odometer, price/gal and it gives me a whole bunch of nerdy info. My evic says I get 15.1 on highway but hand-calced showed an adjusted 17.8 but this is in part to my larger tires and un-adjusted speedometer (I have the conversion in the equation to adjust for large tire size for summer and revert back to stock equation for winter tires)

Probably right, never hand calculated it, I'll do that next time I fill up, but I will fill up with Chevron or she'll next time...

Another thing I was thinking, with my new commute I'm driving the dart alot more. The truck sits alot during the week, I'm wondering if that is effecting anything

Sent from my SAMSUNG-SM-G935A using Tapatalk

Casper · Jul 31, 2017

PCT said:
Past few months I have noticed my mpg in the trash! Cruise control set at 70 on flat ground I'm getting 11-13, where I used to get 14-17. Engine seems to struggle to stay to speed while in 6th. Truck seems to produce power alright when giving it throttle, no hesitation not worried about not making a merge or what ever on free way, it's just when crusing. Truck does fine in city, and idles very very smooth.

According to evic i am at 203 coolant temp while on highway. (Oil reads -43) for some reason the 4.7 doesn't report oil temp. Trans temp at 153.

Ambient has been 80-105

I have used half a can of seafoam through intake (spray version). Cleaned air filter, put oem air hat back on, put a full can of seafoam in gas tank. Upper set of plugs have been done 10k miles ago, all fluids on drive line have been flushed or changed. I take great care of my vehicles so almost everything required has been done. I do see a lot of oil mist in the intake manifold, but catch can will fail can smog.... Few things I think are causing, the oil soaked manifold, or when I was loosing my job I used only Safeway gas for about 4 months straight, so maybe the injectors are dirty... Some have mentioned pcv being plugged, and egr being plugged. Gotta pull the pcv valve and clean it, just don't wanna break anything pulling it off. If anyone could steer me in the right direction.

Sent from my SAMSUNG-SM-G935A using Tapatalk

It might be you started in the right direction but didn't finish--you didn't follow full seafoam treatment instructions, its 1 oz per gallon of gas (I have 32 gallon tank, so two 16 oz cans for me). If you were using crap gas for four months that might be the culprit, and the intake cleaning is supposed to be a full can in the intake with a 15 min soak before restart and purge.
If you are seeing an oily intake you may want to remove your throttle body and clean it using a rag with brake cleaner (never spray, and not TB cleaner). Be gentle replacing TB so as not to strip your manifold threads.

What about the other set of plugs? If they're old that could be an issue too.

What condition are your plug wires in? Any inadvertently make contact with yoru exhaust manifold?

PCT · Jul 31, 2017

Casper said:
It might be you started in the right direction but didn't finish--you didn't follow full seafoam treatment instructions, its 1 oz per gallon of gas (I have 32 gallon tank, so two 16 oz cans for me). If you were using crap gas for four months that might be the culprit, and the intake cleaning is supposed to be a full can in the intake with a 15 min soak before restart and purge.
If you are seeing an oily intake you may want to remove your throttle body and clean it using a rag with brake cleaner (never spray, and not TB cleaner). Be gentle replacing TB so as not to strip your manifold threads.

What about the other set of plugs? If they're old that could be an issue too.

Alright I have another can of seafoam that I was going to run through the vac line, but I'll dump in gas tank. I'll run good gas for a bit and see if it changes at all. I never understood why cleaning the oil residue off the TB helps fuel economy if you don't mind explaining. Also the lower plugs are to be done at 100k

Sent from my SAMSUNG-SM-G935A using Tapatalk

huntergreen · Jul 31, 2017

PCT said:
I have no idea, how would I know, and what do I want to happen?

Sent from my SAMSUNG-SM-G935A using Tapatalk

When cruising on the hwy, look for fluctuations in the RPM , such as the needle bouncing. You should have a slipping feel if this is the issue.

PCT · Jul 31, 2017

Is it noticable while driving or noticable just by looking at tac?

Sent from my SAMSUNG-SM-G935A using Tapatalk

Casper · Aug 1, 2017

Your TB controls admission of air to support combustion. Its fly by wire so PCM can be thrown off when response is lagging.

If TB is varnished, the butterfly can stick. Typically effects acceleration, but could also hang up on deceleration. Not saying this is the only issue, just something DIY you can eliminate that may be a contributing factor.

huntergreen · Aug 1, 2017

PCT said:
Is it noticable while driving or noticable just by looking at tac?

Sent from my SAMSUNG-SM-G935A using Tapatalk

depends on how extreme the condition is, but i would say both, feels like a loss of drive power, sometimes settle and very brief sometimes very obvious. again on the tack some times just a small increase in RpM, sometimes a big jump.

PCT · Aug 1, 2017

huntergreen said:
depends on how extreme the condition is, but i would say both, feels like a loss of drive power, sometimes settle and very brief sometimes very obvious. again on the tack some times just a small increase in RpM, sometimes a big jump.

Sounds good, I'll be aware.

I have been researching, is it possible the o2 sensors are starting to fail?

Sent from my SAMSUNG-SM-G935A using Tapatalk

Garbage freeway fuel econ

2019 2500 6.4

Senior Member

Senior Member

2019 2500 6.4

2019 2500 6.4

2019 2500 6.4

Senior Member

2019 2500 6.4

Senior Member

Senior Member

2019 2500 6.4

Senior Member

2019 2500 6.4

U.S. Navy (Ret.)

2019 2500 6.4

Senior Member

2019 2500 6.4

U.S. Navy (Ret.)

Senior Member

2019 2500 6.4

Similar threads

Forum statistics

Share this page