I just replaced my stock tires to a larger size (P275/70 to P295/70). I noticed that the computer calculated milage is off. The difference isn't that noticeable but I'd kinda OCD. The Ford dealership wants $100 to flash but won't guarantee that flash will take. I'm willing to pay the money, but not if flash won't work. Does anyone else have a do-it-yourself suggestion?

 

find another dealer

 

My local dealer quoted me $140 but didn't sound uncertain about it all. It just wasn't worth it to me, so I passed. I have TorquePro app and use GPS for speedo and hand calculate the mileage with the rpm difference in tire size

 

Might take some work to get the correct coding for a 2001 or a 2008, but people are working on using FORScan for it:
https://www.ford-trucks.com/forums/1...l#post16787790

i fixed mine with an SCT tuner.

 

I don't know what year your working on, but I know 11-16, the dealers can only program for available factory sized tires. So you will have to find the closest diameter tire they offered(go with the larger size, it will be close to accurate). I have a friend with the dealer software. I went with the 34.1" 20" tires for my 37's and I'm off by 5%. Close enough for me. Hypertech makes an in line module that goes behind the cluster that will allow for any size tire. I believe it uses revolutions per mile. 5 star tuning sells it for just over $200. Your only other option is like whats been said, get familiar with forscan.

I have no idea what the dealer means by they can't guarantee it to work. It should take them less than 5 minutes and it's stupid simple. Sounds like the service writer has absolutely no clue.

 

Perhaps an FT member who has the equipment and is local to you, can help you.

What year is your truck, and where are you located?