6.4 MPG dropped suddenly

[Thendrix]

According to my lie-o-meter my MPG dropped about 1 to 1 1/2 MPG in the last day or two. Haven't changed my driving style, no towing done, bought gas in the same place I have been. Truck has 59,000 on it and I just changed the oil. I used Mobil 1 0w40. I haven't had the truck very long. Think I put about 3k miles on it. I'm going to change the air filter just because I don't know when it was changed last. It's not nasty but not clean either. Any other thoughts? We're leaving for the beach Friday pulling a TT so I'd like to see some improvement before then. I've been driving more like an old lady for the last 20 to 30 miles trying to get it back up and no help. Thoughts?

 

[MADDOG]

Check your throttle body and clean it if necessary.

 

[Thendrix]

Will do thanks

 

[NCRaineman]

How about that summer heat?

Over the past two weeks daytime temps here have been steady in the mid 80's to low 90's. I've been using the A/C much more and have dropped 1-1.5MPG average just from riding with the A/C on and idling the truck with A/C on in the afternoons to cool it down before I get in.

 

[mtnrider]

I know some people claim their meter is close to hand calculated but mine is all over the place most of the time. It's anywhere from 1 to almost 4 high. (never been closer then 1 high). Same driving conditions, tank to tank I can vary a couple mpg according to the meter but hand calculated is pretty close to the same.
With only 3k that you have driven the truck you don't have a big sample size of your driving style to go by either.

.

 

[mtnrider]

And NCRaineman has a good point on the AC, it's been hotter than a hoochie ******* here in Georgia the past couple weeks so that AC is working overtime.

 

[RoadRamblerNJ]

According to my lie-o-meter my MPG dropped about 1 to 1 1/2 MPG in the last day or two. Haven't changed my driving style, no towing done, bought gas in the same place I have been. Truck has 59,000 on it and I just changed the oil. I used Mobil 1 0w40. I haven't had the truck very long. Think I put about 3k miles on it. I'm going to change the air filter just because I don't know when it was changed last. It's not nasty but not clean either. Any other thoughts? We're leaving for the beach Friday pulling a TT so I'd like to see some improvement before then. I've been driving more like an old lady for the last 20 to 30 miles trying to get it back up and no help. Thoughts?

Got 14k on mine and it gets anywhere from 10.5 - 12 mpg no matter how I drive. Granny or Speed Demon, does not change. Thats the 6.4 2500 way.

 

[mtofell]

According to my lie-o-meter my MPG dropped about 1 to 1 1/2 MPG in the last day or two.

This amount of change and time period is pretty minor. I'd actually be surprised if your MPG never varied more than this during the course of your normal travels. There are plenty of things like wind, inconsistency in fuel, stopping for construction, etc, etc. that could easily account for such a small change. The first thing I'd do is let some more time pass to see if the drop is permanent. Also, in order to really know what is going with MPGs you should start hand calculating.

 

[Thendrix]

Ok. Thanks y'all. I'll keep watching. Yeah it's been hot as Hades here to. I run a chicken farm for my in-laws and with market age birds in this heat it's really hard to keep them cooled enough to keep eating and gaining weight. You NC guys don't know anything about those chicken farms do you?

 

[14RAM4X4]

How about that summer heat?

Over the past two weeks daytime temps here have been steady in the mid 80's to low 90's. I've been using the A/C much more and have dropped 1-1.5MPG average just from riding with the A/C on and idling the truck with A/C on in the afternoons to cool it down before I get in.

I'd say A/C is the culprit. With hot temps the compressor kicks on a lot more. More load on the engine, more gas consumption ... Although it's hard for me to tell, I use AC like 8 or 9 months outta the year in S. Texas. The coolest it's been the last 7 days was last Monday @ 98*. It's been in the 100's since. Today it's supposed to get up to 105*.

 

[hotrod45]

My bet would be on idling it. If you sit in an idling truck, watching the average mileage display, you'll see it counting down the tenths of a mile-per-gallon fast enough to make your head spin.

 

[brad325is]

Mine did the same thing....kicked the wife out...back to normal.

 

[SouthTexan]

Hot less dense air = less engine power

Which means more throttle is needed to do the same work especially with an ac compressor on all the time to keep the cab cool.

Plus the engine has to pull timing to deter knock which makes the engine run less efficiently. There is a reason why owners manuals recommends higher octane in hot temps or high load because that is where you will see the benefit of the engine not having to retard the timing as much as it would with lower octane fuel. At cold or normal temps, using a higher octane will probably not have that much of effect versus regular octane because it can run this fuel without pulling timing. The higher the temps the more of a difference it makes which is why some see/feel a difference and others do not due to the temps and other variables that each person drives in.

 

[Jkeithnb]

its been hot as h^ll here and my mileage has dropped

 

[bigdodge]

Wind will really kill the mileage on these trucks I've noticed. That's been my experience

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[River19]

Wind will really kill the mileage on these trucks I've noticed. That's been my experience

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Yes, they have the aerodynamic cross section of a dumpster......like all large rigs. And of course we like our leveling and larger tires etc. All of which combined with summer temps and wind make for not so Prius-like fuel economy...... Summer heat and gassers is like what I would see with winter diesel previously..... 1-2mpg gone.

 

[Thendrix]

Thanks everybody. We've been back from vacation a couple of days and the temps are a little better and so is the MPG so I'm guessing you guys are right about the compressor

 

[22hemi13]

Wind will really kill the mileage on these trucks I've noticed. That's been my experience

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The wind. Oh man with the 5.7 in mine when it’s a head wind I turn the fuel Econ page off. It hurts

 

[kirkcad]

My bet would be on idling it. If you sit in an idling truck, watching the average mileage display, you'll see it counting down the tenths of a mile-per-gallon fast enough to make your head spin.

I can vouch for this. It's been hot(for Oregon) here lately, too...90s. A few times I fired up the truck to cool it down before heading out, and yea, that average mpg drops like a rock when it is just sitting there idling with the ac going full tilt. (This was before the camping trip my wife took with it)

 

[NCRaineman]

Ok. Thanks y'all. I'll keep watching. Yeah it's been hot as Hades here to. I run a chicken farm for my in-laws and with market age birds in this heat it's really hard to keep them cooled enough to keep eating and gaining weight. You NC guys don't know anything about those chicken farms do you?

I know of at least ten chicken farms within a 5 mile radius of my home.