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Discussion Starter · #1 ·
Installed the 87 octane canned tune and shut off the AFM, then drove from Gilbert AZ to Las Vegas NV and back which is a little more than 300 miles each way.
AND I drove with the CC set at ten over the speed limit which means I was doing 75 or 85 wherever possible.
After resetting the MPG, I averaged 18.5 MPG driving there and, after resetting it again, I got the same MPG coming home.
Before the tune and disabling the AFM I was lucky to average 16.1 on the same trip or to San Diego.

Now I can't wait to get a custom tune!

I'm curious tho, if I had left the AFM on, would I have gotten even better mileage?
Until I shut off the AFM, I drove with the tranny in 5th gear (which disables the AFM) unless I was on the highway.
Or is it not worth it in the long run?
 

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· Supr Moderator AutoTech SS-Guru Mbr Extraordinaire
2015 High Country Duramax
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I would leave AFM off personally.

But are you just basing your milage off what the truck says or are you calculating it yourself? The only way to get the most accurate mpg average is to do it yourself.
 

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That`s good news but I din`t know how many are getting better gas mileage? I have not but some are. But I will say if it did get better you will be amazed how well it will be with a Lew tune well worth the money get a hold of him his service is top notch and before you know it you`ll have the tune and be happy.
 

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Discussion Starter · #4 ·
The mileage was what the truck told me.
Even if it wasn't totally accurate, it was still a pretty good increase......

Yea, I'm really lookin' forward to a custom LewTune.
Hard to believe it can still get better!
 

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Two weeks after I bought my truck my father-in-law passed away and the funeral was held in Whitley City, Kentucky. We live in Pinellas Park, Florida. Checked all fluids and pressures then hit the road. I didn't know about AFM at the time so it was on. Calculating MPG using mileage, gallons at the pump and a calculator I averaged 26mpg. It was a 15 hour road trip each way. I was ecstatic to see such numbers from a pick up truck. A week later I checked the oil and it was a 1/2 quart low. That's when I came on here and discovered the evils of AFM and how to disable it. 26mpg is nice but not at the cost of a motor and stress headaches.
 

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wehowardjr said:
Two weeks after I bought my truck my father-in-law passed away and the funeral was held in Whitley City, Kentucky. We live in Pinellas Park, Florida. Checked all fluids and pressures then hit the road. I didn't know about AFM at the time so it was on. Calculating MPG using mileage, gallons at the pump and a calculator I averaged 26mpg. It was a 15 hour road trip each way. I was ecstatic to see such numbers from a pick up truck. A week later I checked the oil and it was a 1/2 quart low. That's when I came on here and discovered the evils of AFM and how to disable it. 26mpg is nice but not at the cost of a motor and stress headaches.
Sounds like something is wrong with your calculations. 26mpg from a 5.3L with or without AFM is about 5-6mpg higher than I have ever heard of on a trip long enough to actually have any accuracy. OP has a slightly newer truck with the same engine and is reporting 16.1mpg. I've got close to half a million miles on 5.3l though they are the older Vortec and never seen more than about 21 on any 5.3. Even a 2wd 4.8 is not going to pull those numbers that I have seen.
 

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Nothing wrong with my calculations. I thought the same thing so I had my wife look at the numbers and do her own calculations, she came up with the same numbers. It wasn't 26 for every highway mile, it dipped to 22 and 24 after a couple fill ups but the highest was 26. It happened that one time back in October 2015. Doesn't matter if you believe me or not.
 

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Was just the way it was written and I read it. Thought you meant you were getting that as an average. Heck, take into account the time most of us spend in traffic, city or slow moving roads, and I bet most people see their average much lower.
 

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On our way up traffic was bumper to bumper in Atlanta, GA. It took a little over 3/4 of a tank to get where we stopped just south of Atlanta ti fill the tank. After getting thru the 10 miles or so of Atlanta traffic we used a 1/2 tank. UNBELIEVABLE! I am originally from the Chicago area, I thought Chicago traffic was bad. Not even close.
 

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Haha. I lived in Atlanta for a few months last year. Could not take the traffic. My 7 mile drive to work took an hour and a half minimal. Was faster to walk out the back door and cut through the woods than drive. I hear people talk about how bad the traffic is where they are all the time. Many name cities I know traffic does not compare at all.

Back to OP. I wonder if the high octane tune will increase any or actually decrease fuel consumption. Would be interesting to hear a comparison.
 

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Fisger8new said:
Haha. I lived in Atlanta for a few months last year. Could not take the traffic. My 7 mile drive to work took an hour and a half minimal. Was faster to walk out the back door and cut through the woods than drive. I hear people talk about how bad the traffic is where they are all the time. Many name cities I know traffic does not compare at all.

Back to OP. I wonder if the high octane tune will increase any or actually decrease fuel consumption. Would be interesting to hear a comparison.
The increase by the OP is impressive and good to see. Personally, I wouldn't go for the high octane tune to gain some mpg. It would never be worth it on a cost basis. Based on price spreads in my area, and using the OP's results on 87 tune, one would have to gain 4 mpg on premium just to break even on the cost per mile for fuel. To gain 4 mpg with the Premium tune would be pretty unrealistic. There may be other reasons some may want to use the premium tune, but for some form of cost benefit won't be it. MPG improvements are psychologically soothing, but if there is no cost benefit, it is pretty hollow. For the OP, stick with what you did and continue to track.
 

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wehowardjr said:
Two weeks after I bought my truck my father-in-law passed away and the funeral was held in Whitley City, Kentucky. We live in Pinellas Park, Florida. Checked all fluids and pressures then hit the road. I didn't know about AFM at the time so it was on. Calculating MPG using mileage, gallons at the pump and a calculator I averaged 26mpg. It was a 15 hour road trip each way. I was ecstatic to see such numbers from a pick up truck. A week later I checked the oil and it was a 1/2 quart low. That's when I came on here and discovered the evils of AFM and how to disable it. 26mpg is nice but not at the cost of a motor and stress headaches.
I have to have more information on how the hell you got 26mpg. I have owned cars that didn't get that kind of mileage. How fast did you drive? Was it downhill all the way there? Tailwind?
Sorry Butch, just never seen one of our trucks get that kind of mileage.
OP....didn't mean to high jack your thread. I have yet to get my Lew tune but I had one in another truck I had and your gonna love it!
 

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What you fail to realize is over time you wont be getting that sorta mpg. I have 285's, a 2.5" level and have run both the 87 and diablo tune. They always start off high, approx 17mpg, and then within about a week or two it dips to 14-15mpg and it stays there.

AFM is off, trans firm shift on, shift points are adjusted and I have a heavy foot.
 

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Best mileage I've been able to get was 21.9. And that's trying. The problem was most likely the gas pump. The best way to test is over several tanks. I usually use the computer though if I'm not tracking it. It's very close to my calculation. Actually it says its less usually my .1 or so.
 

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Discussion Starter · #18 ·
For wehowardjr and Fisger8new:

18.5 was my overall average each way, NOT the best I saw during the trip.
I reset the MPG's to 0 before I left my driveway, and when I pulled outta the hotel on my return trip.

Now that I'm back home, after I reset MPG's to 0 again, around town I'm lucky to keep the average at 14 or better and that's watching it and trying to keep my foot out of it......
 

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05Canuck said:
How fast did you drive? Was it downhill all the way there? Tailwind?
Sorry Butch, just never seen one of our trucks get that kind of mileage.
OP....didn't mean to high jack your thread. I have yet to get my Lew tune but I had one in another truck I had and your gonna love it!
It was pretty much flat roads all the way until we got closer to Chattanooga, which we averaged 73mph on until we reached Atlanta, then the mileage went down going up and down so many hills. There might have been a tailwind because a storm was following us most of the way and finally caught up with us north of Knoxville. I remember because we had some cardboard boxes filled with some stuff in the bed for our grand daughter that got soaked. Like I said in my post, I was ecstatic over the mileage but it only happened that one time. It was no mistake. I would love to try it again but that was, and still is, the last time I spend so much time behind the wheel. LOL I retired from OTR driving and want no more to do with it. LOL
 

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CheezyRiderAZ said:
For wehowardjr and Fisger8new:

18.5 was my overall average each way, NOT the best I saw during the trip.
I reset the MPG's to 0 before I left my driveway, and when I pulled outta the hotel on my return trip.

Now that I'm back home, after I reset MPG's to 0 again, around town I'm lucky to keep the average at 14 or better and that's watching it and trying to keep my foot out of it......
Since installing the tune I don't even get 14 around town or on the highway. I can't keep my foot off the pedal.

My last fill up showed an average of 10.7mpg. LOL I honestly don't care because it was fun.
 
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