gas milage differance

[fang16]

2015 5.3 z71. Going the same distance, same speed (cruise control @ 79), same load, same traffic, same radio station etc. Everything is a constant even where I get gas but there will be as much as almost 3 mile to the gallon difference in mileage. I have it set on the 25 mile average setting. 9400 mile on truck.

Should I run some kind of fuel system cleaner? sea foam ?

[newdude]

2015 truck with only 9400 miles? What kind of driving do you do with the truck? Lots of idle time? Highway? City? Mixed? What octane are you running? Any E85?

 

The 25 mile average shows you just that, the mileage you are getting over a 25 mile distance. Not an accurate gauge to what kind of MPG you are getting. More accurately would be the 400 mile MPG or if you reset either your Trip A or Trip B every time you fill up and see the miles traveled between fills and it also shows the average MPG for that trip distance.

[O_J_Simpson]

How are you calculating your results?

[Sierra706]

2015 5.3 z71. Going the same distance, same speed (cruise control @ 79), same load, same traffic, same radio station etc. Everything is a constant even where I get gas but there will be as much as almost 3 mile to the gallon difference in mileage. I have it set on the 25 mile average setting. 9400 mile on truck.

Should I run some kind of fuel system cleaner? sea foam ?

Summer vs winter gas, headwinds, air temperature, tire pressure, tire wear, what side of the bed you woke up on, etc..... can all factor into mileage.

 

 

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[The Zip]

I drive the fullsize SUV, so don't know if the PUs have AFM. Since you mention everything is the same, sounds like AFM may be a player and not dropping cylinders for fuel management.

[fang16]

I'll keep an eye on the AFM next trip.

[Silver16]

Good gas mileage + truck= not a truck

[Spurshot]

Summer vs winter gas, headwinds, air temperature, tire pressure, tire wear, what side of the bed you woke up on, etc..... can all factor into mileage.

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What he said above.

 

The electronic measurement system on our trucks will give accurate information and I do believe the OP is getting that big of swings in mileage, when those specific slices of data are taken. As pointed out above, wind, temperature, and other factors can change mileage. It's normal and expected.

[tnchevy]

The 25 mile average is not going to tell you much. You need to hand calculate the mileage at every fill up and keep a record of it. The more mpg's calculations you do the more accurate your over all average will be. After 3 years and 20k miles I am at 19.2 mpg's running average.

[fang16]

Most of you missed the question. If everything is the same on a 120 mile round trip why does the mileage very so much? This is a weekly trip. Just up there and back. No other running around. I have seen it get 15.4 up to 21.5 on the same trip.

[Nanotech Environmental]

Most of you missed the question. If everything is the same on a 120 mile round trip why does the mileage very so much? This is a weekly trip. Just up there and back. No other running around. I have seen it get 15.4 up to 21.5 on the same trip.

Headwinds/tailwinds and air temp will have a noticeable impact.

[Dnt]

If you reset your trip A or Trip B at the start of each 120 mile leg you will see more accurate results. The least little thing such as a extra 5 minutes idle or a strong tailwind or head wind can drastically change with a 25 mile average, just not enough miles to establish a use-able average just creates a Moving Target LOL. What have you got over a few thousand miles average?

 

[The Zip]

OP said everything was the same (headwind, tailwind, tire pressure,...), has to be something going on with the truck. Don't know if the dealer can tweak AFM to see if that will make a difference, call the service tech and ask the question.

[Spurshot]

Most of you missed the question. If everything is the same on a 120 mile round trip why does the mileage very so much? This is a weekly trip. Just up there and back. No other running around. I have seen it get 15.4 up to 21.5 on the same trip.

 

What you are seeing on the truck's DIC with it set at 25 mile average, is the fuel economy for just the last 25 miles at the time you view it. So, when you get to the end of your 120 mile trip and view this information, it's just a log of the last 25 miles, not the whole trip. I think someone pointed it out earlier, you should reset your trip odometer to zero at the beginning of each trip, which also resets a trip fuel economy logger, and then you can read the fuel economy for the trip at the end, then compare trip fuel economy from one trip to another. I think you find it's very close.