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Discussion Starter · #1 ·
From reading on different threads you are allways seeing how alot of these trucks get alot different MPG between trucks.

Even when the make up of the trucks that are close to the same being with a 3.73 gearing and mostly stock.
Is there much that can be done if you got a truck that is getting 14-15mpg highway driving that don't cost alote of money.

This may be a dumb question but, is there any way when looking to buy a truck other than trusting the person selling it if it will be good on fuel.
Thanks
 

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My truck gets 14 mpg city, about 16-18 hwy. Depending on if I am happy that day or depressed and drive slow... Lol. I have a 5" turbo back, just got it yesterday so I am anxious to see if I gain any mileage. And a k&N crappy cai. and a smarty jr tuner.

Best I can say
 

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all depends how u drive and where u live.. some people live in hilly areas.. and some live in flat land.. some people drive like there running from the cops some drive like they dont know where the pedal is.. some have more mods some have less mods.. so yea everyone will be different..

and blood.. i just added my 5" TBE with no cat or muffler.. noticed about 1mpg so far in city driving.. havent tested highway.. but im going on a 70 mile trip tomorrow on highway..

ooo and im getting 17.7 city so far..
 

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all depends how u drive and where u live.. some people live in hilly areas.. and some live in flat land.. some people drive like there running from the cops some drive like they dont know where the pedal is.. some have more mods some have less mods.. so yea everyone will be different..

and blood.. i just added my 5" TBE with no cat or muffler.. noticed about 1mpg so far in city driving.. havent tested highway.. but im going on a 70 mile trip tomorrow on highway..

ooo and im getting 17.7 city so far..
Im starting to think its my air intake, its completely filthy, and I clean it once a week, but it was used in the desert to pull and the guy who had it before me never cleaned it. Its a K&N cai, not sure if I should replace it with a AFE stage II or what... Lol But I have the same truck as you with a 5" lift 35 toyo m/ts and 410s in the rear. What do you run your smarty jr on? What setting timing and tq? I have a muffler but no cat...
 

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im running SW3 TM4 TQ2... i need to clean my airaid.. came with the truck.. i wanna get something different but its not huge have to on my list.. oo and my light on the pedal..
 

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Same setting I run, have you brought yours to a dyno yet? I am wondering what numbers mine makes. I just stuck it on sw#1 yesterdya but it runs odd. Not as powerful but still fast but I dont like it. Anyway ya I try to be light on the pedal, just cant sometimes.
 

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nope no dyno.. and i dont plan on doing one anytime soon.. im broke lol..
 

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nope no dyno.. and i dont plan on doing one anytime soon.. im broke lol..
Also I dont know what your version of "City" driving is, we have a f****n stop light every 200 ft where I live, its really annoying.
 

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i get on and off highway for like 5-10 mins then sit in traffic and traffic lights every 500ft..
 

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Im starting to think its my air intake, its completely filthy, and I clean it once a week, but it was used in the desert to pull and the guy who had it before me never cleaned it. Its a K&N cai, not sure if I should replace it.
Ditch the k&n. I'm not going to say I know a lot about the ins and outs of diesels but the k&n is crap. Had one on my 03 7.3 ford and cleaned it every month and still dusted the turbo. From what i read a dry filter is the way to go. My 2 cents.
 

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I second the getting rid of your kandn unless you want to ruin the longevity of your cummins
:agree2: they arent worth a crap on a turbo diesel.
 

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I was getting about 17 MPG when I first got my truck. I changed to a K&N and am running an Edge Max. I went to 40 miles north and back to Seattle from Coeur d'Alene, ID and averaged 20.75 MPG. Drove there and back on less than a tank of gas (almost 700 miles). The point is that how you drive and what you got under the hood can make a big difference on mileage. At one point I was getting almost 22 MPG. general principles: air in, air out. How much air you got going into the turbo as well as injector pressure and timing make the difference, at least for me.
 

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I have an '03 and an early '04 both 6 spds both 3.73's. '03 get 12-13 maybe the '04 gets 17-18. My buddy claims he used to run an OTR truck for an outfit. They bought like 20 identical semi trucks at one time and he more or less ran everyone of them depending on the run he was on. He claimed some trux had more power and better mpg reguardless of the load and area of travel. He claims truck engines are like the women he dated. They all had the same parts, some just performed better than others.
 

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The biggest difference is climate/terrain for the same driver to account for fuel mileage differences.

But the biggest difference in fuel mileage -- all other things the same -- is the driver. Cummins says the spread between professional drivers is 30%.

The only valid comparisons, then, are between stock trucks of the same spec. The difference at that point is minor in comparison to the above.

Is there much that can be done if you got a truck that is getting 14-15mpg highway driving that don't cost alote of money?

For the highway: stock truck, highway rib tires with factory pressure and balance, fresh filters/fluids; great alignment (and no steering play), no brake drag. Travel speeds above 60-mph kill mpg, so ease onto highway (don't accelerate past 50 mph, just ease up to about 58); set the cruise and maintain steady state. Know stops beforehand (plan), ease in & out of them. No idling, ever. Bed tonneau cover helps, as does a winter front (even in Texas as it isn't winter fuel, but winter temps that hurt mpg). Use block heater with 40F temps, again, no idling, just ease down the road.

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Also, I wonder how many trucks are actually programed with the right tire info. Driving through construction areas with radar speed indicators, I noticed I was always 10km/hr slower than what my speedo said. I went to a buddies dealership, stole the starscan tool and found out that NONE of the the options were right. My truck was programmed with something like a 9.25" diff and 235 tires. Set it all up properly and the speedo is now bang on,,,, but my mileage droped a couple points.
 

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so many variables. down to tolerances on bearings/gears/etc in the axles, hubs, transmission, engine crank case, etc.

couple that with fuel quality, driving style, and climate

oh, and don't forget the fact that next to "fish" size, fuel mileage is the top thing people tend to exaggerate about
 
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