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Discussion Starter #1
I've been running the Spartan 250 tune for 18,000 miles.

All of the following mileage numbers are hand calculated.

Based on my particular in-town driving habits (which are very consistent day-to-day), my mileage was always 11 to 11.5 mpg, starting from the time I did the tune and delete (600 miles) to 14,000 miles.

At 14,000 miles my mileage began to increase for a few tanks of fuel, then leveled off at 12.5 mpg. I was very happy, especially because it was during the winter months and the fuel was probably winter-blend!

At 16,500 miles my mileage began dropping back to the 11 mpg range. I loaded the 210 tow-tune for a tank, just to see what it would do and only got 9 mpg. Loaded the 250 again and am still seeing only 11 to 11.5 mpg.

Where is my extra 1 to 1.5 mpg!!!!!!!!!!!

Oil and filter changed every 3,000 miles. The last fuel filter(s) change was at 15,000 miles, tire pressure is set at 65 psi (check it every fill-up) and my "Green" filter looks as good as the day I dropped it in.

Any thoughts or ideas?
 

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3.55 gears

All driving is "in-town" stop & go traffic.
I hate to say it but our Honda Minivan gets 11-13 around town, maybe this is good for a 4 ton vehicle. I am at 22.5 MPG mixed with the Spartan 275 and S&B CAI. 3.73. gears CC SB 4x4. I was at 18 with just the CAI and 16.6 before anything was done.
 

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I hate to say it but our Honda Minivan gets 11-13 around town, maybe this is good for a 4 ton vehicle. I am at 22.5 MPG mixed with the Spartan 275 and S&B CAI. 3.73. gears CC SB 4x4. I was at 18 with just the CAI and 16.6 before anything was done.
Is that calculated by hand? 22.5 seem pretty high especially with 3.73. I have the same gears and the best I have seen when my truck was stock height was 15.7 after tune hand calculated. 11.8 was stock MPG hand calculated.
 

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Is that calculated by hand? 22.5 seem pretty high especially with 3.73. I have the same gears and the best I have seen when my truck was stock height was 15.7 after tune hand calculated. 11.8 was stock MPG hand calculated.
Thanks for asking the question for me.

There have not been any substantiated cases of the 6.4 getting this kind of mileage if you are hand calculating the mileage.

The higher the tune, the more the truck's computer lies.

In-town, my truck's computer shows 15 mpg when I'm actually getting 11. I've seen as high as 23.9 on the highway using the mileage computer. Stop, fill-up, hand calculate and get used to disappointment when it is really 17 or 18. This subject has been :bdh:bdh:bdh on this and all the other Forums.

I'm looking for an objective opinion as to why my truck's mileage has changed so much.
 

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Thanks for asking the question for me.

There have not been any substantiated cases of the 6.4 getting this kind of mileage if you are hand calculating the mileage.

The higher the tune, the more the truck's computer lies.

In-town, my truck's computer shows 15 mpg when I'm actually getting 11. I've seen as high as 23.9 on the highway using the mileage computer. Stop, fill-up, hand calculate and get used to disappointment when it is really 17 or 18. This subject has been :bdh:bdh:bdh on this and all the other Forums.

I'm looking for an objective opinion as to why my truck's mileage has changed so much.
I just filled up to the same level as before. I have gone 53 miles and the fuel level reading is at 96.6 %. The gauge is still well on the "full" white mark. 65 mph on flat land with 5, 2 adults and three children. If I keep this rate up I will be at over 600 miles for the tank which is over 20 MPG, not unusual at all. I was at 16.6 with winter fuel and no mods. All hand calculated as My fuel is money at tax time. I went to 18 and a little after the CAI install. This will be the first full tank with the AMsoil Diesel Concentrate and cetane boost as well as all 275 tune. I suppose the only way to show is to film the entire tank and gauge being used. Has anyone done this yet? I have only had 11 miles to the gallon or slightly worse while towing my 33' rockwood trailer with 5 people, two dogs, and a half cord of wood I range from 9.5 to 11 depending on weather, terrain, and my throttle discipline. If that is your mileage around town you have a problem with your truck especially with 15.7 on highway. That is bad stock let alone tuned. My computer has been pretty close, under if anything else thus far. My fuel gauge, Spartan displays and trip odometer are the tools I use.

My truck would be gone if I only got 15.7 and 11.5 respectively, or repaired. Please do not dispute my findings based on your experiences. I drive well, perhaps you do not, I maintain my vehicle, perhaps you do not. I have to espouse those that can suddenly recall their vehicles fuel mileage from a while ago before they were modded. I know of some that modify tires, ride height etcetera, and are mad that their mods do not work out too well once they tune it( having expected to get some MPGS back) Some (one in particular) raised their truck, put larger tires and put on some bumpers and saw they were getting 8 MPG. They tuned it saw a small jump to 11 or 12 and then ranted online because they were thousands in the whole and stuck. If accusing me, or others (indirectly) of not knowing how to calculate mileage or of BS makes you feel better, great do it. I for one, am proud of my mods, can now afford to camp this season, and love the look of black smoke out the tail pipe. :happydance


Dirtymec asked if you had 4.88 gears for a reason. Think about that.
 

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Thanks for asking the question for me.

There have not been any substantiated cases of the 6.4 getting this kind of mileage if you are hand calculating the mileage.

The higher the tune, the more the truck's computer lies.

In-town, my truck's computer shows 15 mpg when I'm actually getting 11. I've seen as high as 23.9 on the highway using the mileage computer. Stop, fill-up, hand calculate and get used to disappointment when it is really 17 or 18. This subject has been :bdh:bdh:bdh on this and all the other Forums.

I'm looking for an objective opinion as to why my truck's mileage has changed so much.
I am not sure why your has changed so much. Mine is pretty consistant at every fill up. I get about 13-14 with the 6"lift and 37"tires. I logged every fill up for over a year on my iPhone so each tank was hand calculated
 

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I am not sure why your has changed so much. Mine is pretty consistant at every fill up. I get about 13-14 with the 6"lift and 37"tires. I logged every fill up for over a year on my iPhone so each tank was hand calculated
Tuned truck too? If so when?
 

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I have had a total of a 36% increase in fuel economy from CAI (8% increase) and the rest from the DPF\DOC delete, 275 tune and Amsoil Cetane and Diesel Concentrate. Not at all unreasonable when you crunch the numbers. 50% or higher gain is in the realm of skeptical IMHO. From forum searches I have found my readings to be quite usual if not the norm.
 

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Before or after tire and height mods or both is what I meant, sorry.
11-12 stock, 15-16 tuned, 12-13 tuned w/lift and tires.

I have had a total of a 36% increase in fuel economy from CAI (8% increase) and the rest from the DPF\DOC delete, 275 tune and Amsoil Cetane and Diesel Concentrate. Not at all unreasonable when you crunch the numbers. 50% or higher gain is in the realm of skeptical IMHO. From forum searches I have found my readings to be quite usual if not the norm.
I have been reading 4 forums for over a year and I believe 22 mpg is not the norm. I am not doubting you since you seem to have been monitoring your fuel usage. I am just giving my example from over a year of logging EVERY fill up. I am very easy on my truck and am religious on my maintenance with proof of everything. I am not complaining at all about my mileage and never have. I am just posting my year of research on MY truck.
 

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11-12 stock, 15-16 tuned, 12-13 tuned w/lift and tires.



I have been reading 4 forums for over a year and I believe 22 mpg is not the norm. I am not doubting you since you seem to have been monitoring your fuel usage. I am just giving my example from over a year of logging EVERY fill up. I am very easy on my truck and am religious on my maintenance with proof of everything. I am not complaining at all about my mileage and never have. I am just posting my year of research on MY truck.
I understand. For reference i am one of 7 persons in a ;pretty tight group of guys whom own a 6.4 3.73. Your mileages, tuned or not, are below any we have seen or experienced. 11 or 12 stock is what our camping bud sees with his 350 DRW 4.30 Stock. I would be upset and ripping my truck apart trying to find a problem if i only got 15 stock. Granted most of my driving is highway, still my worst tank ever was never close to your best tanks. I will do a drive to Ocean City, MD and back to my house and see what I get. I have done this in my old set up and remember where I filled up at. No computer, tuner display, or other force can alter ( too much anyways) how far I get on the same amount of fuel. I have a reliable benchmark, as I almost always fill up before sunrise, at the exact same station at the exact same pump( 0330 hours has few people out and I always hit the second pump from entrance to leave room. I set the nozzle on the middle lock and go until it pops then stop. It is almost always 26.2-27.0 gallons depending how long I was on empty. .08 of a gallon difference is worked out over time. Winter fuel is .6 MPG less than summer when I was getting almost rock solid 17.4 MPG. Correction from earlier, "18" with CAI was 18.4. I just went through my logs and found the numbers.

You can chart my course from Easton, MD to Washington, DC and back with little traffic and 5 miles a day in between work of local small town traffic. You will see there are only 4 lights until DC I have to deal with for the 65 mile or so ride at 65 MPG on flat terrain. Camping season i here again and this will be my first season with any mods. I will kick off at Tall Pines in VA. I know the route and how far until I fueled up. I will post all findings.
 
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