The "best way" is Smarty. The other way is to go to the dealer that may charge up to $100.

 

Some of the dealers charge about .5 hours. Maybe $55 to change your speedo. Smarty, Bully Dog, and other programmers can calibrate your speedo, and the $55-100 you would spend at the dealer can be applied to a programmer. Another method is to live with it, just take a GPS with you to see yur actual speed. Obviously, he faster you go, the more your speedo is off by....

 

Ouch! Probably not bad for a 2005 but this past week I drove from IN to MD. I filled up in OH after my turn driving and had a hand-calculated MPG of 21.98. Checked it again on the next tank and had 21.10. The key is keeping it under 70 mph. I had the cruise set at just under 70.

I think I'll keep mine for a long time...

 

And if you set the cruise at 65 your mileage gets even better.

 

I'm usually at 75mph. Would a taller tire help lower the rpm to help the mpg?

 

Probably not since taller tires get fat really quick therefore your rolling resistance goes up.

Just to give you an idea, my stock jetta tdi has pizza cutter tires 195s. When I went to 205s, I lost 3 mpg.

Michelin makes an interesting tire - 7.5 by 17 which is skinner than stock tires and 33.5" diameter versus stock 31.6". They are rated for 2800 lbs which is not far off of factory tire load rating of 3000 lbs.

If anyone has tried these, please respond with results. I would assume a 2 mpg increase by using these tires due to lower rpm as well as rolling resistance.

 

The stock tires are rated for 3195 Lbs. Over 4 tires, that 400 lbs difference is going to add up. Be careful going with a tire under the stock load rating, especially if you tow. You should use either a D or E rated tire, both of which normally have around the 3100-3200 load rating (with the E being having the stronger sidewall and what I normally suggest for those who tow often). 2800 may put you in a C rated tire, which does not have the sidewall strength of the D or E... Would make for an interesting tow.

 

The dealer can flash your computer for the 285s for $$ (that's what the PowerWagon uses), but I just took a good long trip with my GPS and found that my 285s put me consisantly about 3.8% under actual mileage, as shown on the GPS. So I add about 4% when calculating my MPGs and try to remember that when the speedo says 100mph I'm really going 104.

(Just kidding, I would never drive 100, or admit to it anyway)

 

My '03 QC 2wd Dually gets about 15.5 or 16 stop and go and anywhere from 18 to 21 on open highway solo, depending on how far I mash the peddle. I have a chip. New on the highway without chip I was getting 16 to 18.

 

I have 285's on my truck, it came with 245's. Using mileage markers on the highway, and checking with GPS over long distances, I figure my mileage is off 7.2%. I don't think the 07's are easily reprogammable for tire size, so I just do the conversion when I figure my mileage. And I write down every drop that goes into the truck. I've been getting 18.2-18.8 MPG all winter.

 

I have a 2003 LB, Quad, 2x4, 5spd, with the Edge EZ chip set at 60hp over. I have gotten as good as 24mpg (hand calculated). I make several long trips - unloaded I average over 20mpg. Loaded (14 ft enclosed weighed down over 6k lbs) I get around 13mpg.