Really really bad MPG...

[king99]

So since i've been playing with my Trinity my MPG has gone down. To be expected with a Hemifever tune, lots of mods and a heavy foot. I went from 14.6mpg stock tune to 12.5 Hemifever 93 octane tune. I could live with that given the gains from the tune. I then put 35" tires on and with the Hemifever tune I was getting 10.6. I then downloaded the backup tune (stock tune) and got 9mpg. I reinstalled Hemifever tune and got back in the 10's. Then downloaded Mileage Booster Tune and I am still getting 10's. I just can't imagine that I would lose 4-5mpg with the 35's. No matter what tune I do I get in the 10's. Any ideas? Dealer reflash of computer? IDk

 

[09SMOKINHEMI]

dang, that's pretty low. did you change the tire size on the tuner too?

 

[Chewy]

Have you tried pulling the negative off the battery and letting it sit for a few minutes, hooking back up and seeing what you get?

Worth a try...

How much more do the tires weigh than the ones you replaced?

 

[king99]

dang, that's pretty low. did you change the tire size on the tuner too?

I did. It keeps telling me it failed to change it but when I look to see what it is set at it says 35. Speedo was off 7mph (speedo 7mph faster than GPS) before I changed it in tuner, now its off 3mph (speedo is 3mph faster than GPS). I even downloaded the newest version which was suppose to have the fix in it for that.

I will try taking the neg off battery, worth a shot.

I don't know what stock tires and wheels weigh in at but 20x9 XD Misfits with 35" Nitto Trail Grapplers weigh 83lbs i believe.

 

[Chewy]

That's a lot of weight to get moving for sure. Are you figuring the MPG or going off the truck? Also, if speedo is off, I imagine your odo is too!


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[Stangshcky12]

Have you leveled your truck?

 

[ramathorn14]

it's lifted.

 

[Hemi450hp]

This is just the downside of a lifted half ton. Mileage goes down very fast once you lift them and add bigger tires.

I had a customer call me yesterday saying that he lost 3mpg simply by installing a front leveling kit. Stock tires with the only difference being the 3" lift up front.

 

[KozzyJr]

This is just the downside of a lifted half ton. Mileage goes down very fast once you lift them and add bigger tires.

I had a customer call me yesterday saying that he lost 3mpg simply by installing a front leveling kit. Stock tires with the only difference being the 3" lift up front.

 

[Stangshcky12]

This is just the downside of a lifted half ton. Mileage goes down very fast once you lift them and add bigger tires.

I had a customer call me yesterday saying that he lost 3mpg simply by installing a front leveling kit. Stock tires with the only difference being the 3" lift up front.

I missed the 3" level and 1.5" BL in your sig earlier but this is what I was getting to
I lost 4-6 mpg leveling a CTD as stepping up to 35s

 

[TXKID]

I get about 9 in the city and 12-13 on the highway I feel your pain bro, but I do have 20x12" rims with 37" tires about 11" of lift and 500 lbs. worth of steel bumpers so I think yours should be a little higher still...

 

[BigDogg795]

This is just the downside of a lifted half ton. Mileage goes down very fast once you lift them and add bigger tires.

I had a customer call me yesterday saying that he lost 3mpg simply by installing a front leveling kit. Stock tires with the only difference being the 3" lift up front.

Holy crap, as if I didn't already have enough reason not to lift...I can't believe the aerodynamics changes that drastically!

 

[mattman_13]

Stock wheels and tires weigh in at 75 according to another post I looked at. I honestly do not see the 35x12.50x20 trail graps and your rims weighing in at 83 sadly. lol
Id say the rims are around 30 and the tires around 80 alone. Just guessing.

I feel your pain though. You're gonna have people saying "what do you expect". lol But I agree with you.

Get this.... I'm pretty sure my fender flares added a decent knock to my mileage! Gonna play around with it when I get home and see what happens. I'd like if someone made an underbody aero dynamic package for our truck for when we lift. something from the front bumper to guide the wind over the cross members and etc. instead of it just hitting the cross members getting chopped. < am I grasping at straws? lol

 

[Rock$tar]

I did. It keeps telling me it failed to change it but when I look to see what it is set at it says 35. Speedo was off 7mph (speedo 7mph faster than GPS) before I changed it in tuner, now its off 3mph (speedo is 3mph faster than GPS). I even downloaded the newest version which was suppose to have the fix in it for that.

I will try taking the neg off battery, worth a shot.

I don't know what stock tires and wheels weigh in at but 20x9 XD Misfits with 35" Nitto Trail Grapplers weigh 83lbs i believe.

With larger tires your speedo should be reading less since your tires are making less rotations per mile. This also causes your mpgs to read low aince your truck thinks you never went as far as you did.

Posted by my Droid

 

[mattman_13]

OH and on your diablo put your tire diameter at 33.5 Thats what I had to set mine at to get my speedo dead on around 50-80. I have 35" toyos

 

[king99]

If GPS is reading 50mph Speedo is at 53mph. Don't ask my how or why but thats what they are reading. Works out wel when I am not paying attention because if i am speeding at least its 3mph less than I think I will have to try 33.5".

I do have it leveled. Pulled out the 3" kit and put in Bilsteins all around. Not that that makes a difference but just figured i'd throw it out there.

In regards to the weight of the wheels and tires i'm sure I was off on that. For some reason I remember seeing someone post that their 35's came in at about 83lbs but again I'm sure I am off on that.

The strange thing is that no matter what tune I have downloaded the MPG is basically the same. You would think that there would be some sort of difference given that different tunes mean difference fuel consumption. I figured i'd at least see a difference running the mileage booster tune.

 

[mile_high]

Sorry to hear this but I'm glad mine isn't the only one. I went from 16.5 stock average to 13.5 on the economy tune. The 91 tune was even worse (but much more fun).

 

[mattman_13]

I'd say with stock tires and a stock setup you would see a difference with the mpg tune. But because the truck has less power and working harder it gets negated with the 35s.
With my diesel truck I'd get amazing mileage with the hottest tunes. More power to get the big thing rollin.
I'm taking my truck back to stock so I'll test out the difference in tunes and post up my findings.

 

[mattman_13]

If GPS is reading 50mph Speedo is at 53mph. Don't ask my how or why but thats what they are reading. Works out wel when I am not paying attention because if i am speeding at least its 3mph less than I think I will have to try 33.5".

If you are doing that then you are also putting more miles on your truck than it actually has on it!

 

[Zevox]

Sorry to hear this but I'm glad mine isn't the only one. I went from 16.5 stock average to 13.5 on the economy tune. The 91 tune was even worse (but much more fun).

The mileage booster tune in my R/T got worse gas mileage than the 93tune did. My truck almost felt like it was straining with the booster tune. It was very odd, guess it was because of my 4.10's?