My thread...

https://www.ford-trucks.com/forums/1...-question.html

 

Did you not read my post about throwing off you odometer with larger tires???

 

Yeah I read it. But 3.0 difference with tires?

 

No 1.5 for tires and maybe .5 with the reading being off. Yes I believe with those tires (315's yes?) and calibration for them you're looking at 8-9 mpgs all around. The odo is off so maybe thats why you're calculating 7. These are thirsty rides and when you dig into their power they drink like crazy.

 

Would the sct 3015 tuner be the correct one to use on my 08?

 

A tuner will NOT improve mpg on a V10 and if it does maybe .5. But that's on a no fun economy tune. I use my truck for hauling and fun. I have a 30mpg beater car for commuting. I know you're trying hard to improve mpgs but in all honesty it's a lost cause with a V10. Add large tires and it's a near impossibility. Sorry man.

 

Tuners CAN be great for certain things like more power for hauling that load or help shift points, but trying to get a bunch more gas mileage isn't their main purpose. You can buy a heluva lot of 87 octane gas for the 4 to 600+/- dollar cost for one of them. Then often there is the need for 91 or 93 octane at a bunch more cents per gallon also the fact that you just plain like to hammer the throttle harder to use those additional horsepower. This is a 7-8000 pound vehicle that needs lots of energy to get it going from a stop then keep that aerodynamically challenged front end splitting air(think barn door aero). And lastly, engine life - and whether any manufacturer want to admit to it, but these tuners do reduce engine life by some amount - even a so-called bullet proof 3 valve V10.

But with that said, it IS your truck to do what you feel you want

 

I was just looking for a tuner to calibrate my speedo to the larger tires.

I'll be going on a long trip so I'm going to write down my mileage and really try to nail down my MPG.

 

Most tuners won't correct the speedo for larger tires since the ABS system in involved. A Ford dealer can correct the speedo. Then with the speedo corrected you can add the tuner which will save that new "stock" calibration.

If you are running 35's and have 3.73s on top top of that it will add a lot more load and rolling resistance for the engine and trans to deal with. The result of the engine/trans working harder will be reduced mpg by an often considerable amount. Add in hills, stop and go driving, etc and the mpg really drops. If you don't have at least 4.30 gears with 35s I would consider a gear change.

Use a GPS to obtain your miles traveled and to verify your speedo is accurate after you get it changed.

 

Heck, just use a GPS as a speedometer as well as odometer. Also you can use to check the truck speedo/odo and calculate fuel mileage.

 

That does not give the PCM the accurate information it should have. Correcting for the larger tires is the right way to do it.

 

I used the Torque app on my cell and on a level road, ok slight downhill, @ 60, if I keep the throttle around 25% and load under 75% I can get 19mpg. As soon as the load hits 80% it drops pretty quick to 14 but I don't know how accurate it is. The lie o meter rarely varies from 11.4.

 

I just bought an 05 CC LWB 4x4 Dually V10 I'm seeing 8.5 on the LOM with stock 245/75/17E tires at 50 psi.

 

For a whole tank best I ever got was 12.5. I can get 19 for short strecthers on my sgii

 

I calculated my fuel over. 1200 miles the last three days and had 7.834 mpg. Half of that was towing a light trailer and the return trip I had 3k lbs on truck and seven on the trailer. Mostly hiway 65 mph.