I recently purchasd BFG 285's for my truck and expected some loss on my MPG. My truck is well maintained and runs fine. With the stock 245's I was getting a solid 15-16 mpg on my daily commute. On trips I could manage 18-19 mpg. I travel 60 miles round trip a day and it is about 85% highway. I'm an easy go'er. 65-70 on the highway and no heavy foot driving at all. I got sucked into the 285 "look" and as expected, with the addition of the 285's I saw a drop in MPG.
I realize my speedometer was off so I never calculated because I was on a trip in Mexico the day after the 285's were put on and utilized my auxiliary tank to fill my main tank for the few days I was down there. I have no guage on my aux tank. After getting back to Texas the very next day I decided to purchase the Hypertech III and install it to mainly adjust my speedometer for the larger tires and hopefully gain some MPG. It seems like everyone sees an improvement with fuel mileage after installing a Hypertech.
I started with level 3 and have been there for nearly a week. Since installing the programer I have seen a drastic drop in MPG. I can't even hit 200 miles on half a tank like I once did. In fact, the truck nearly consumed 3/4 of a tank just to hit the 200 mile mark. I will fill up my tank today and hand calculate but something does not seem right. Has anyone else experienced a drop in fuel mileage after installing a Hypertech III? I set the wheel size to 32". Is that too small? Can half an inch or so throw my odometer off that much? Do I need to drop to level 1 or 2? Any thoughts?

Hypertech does not realy help out with milage, my dad has a 05 and he can get 15 on level-III and drops below stock, on 1-2 levels. He tried the predator on 40hp and now gets 18 mpg, but he has 265 tires.

I was getting a solid 18 and some change on level 3 running 285's.

Its not the programmer. It sounds as if something is wrong elsewhere. Try to change your fuel filter.

285's are 33 inches tall, in fact i think its nearer 32.85 or something around there. That will help your speedo and improve your DIC slightly, but that doesnt really matter anymore as the onboard computer is now useless for calculating MPG since you put the programmer on there. Try bumping your tire size up a little, or better yet, fill up, travel a known distance then fill up again and hand calculate - it seems a little strange that so many, including myself have noticed an improvement in MPG, and you arent......

I have a lly with the hypertech and running 305's. I'm not certain if the on baord electronic reading is accurate, but it reads around 18 mpg most of the time. I did notice a slight increase after installing my turbo back 4" MBRP exhaust too.

measure your tire to know what to put in, I know my BFG 285's are actually 31.5", not 33's as they are portrayed.

I belive hypertech does not state that you will get better mileage on level 3 you may get better mileage or not but dont expect it.On Level 1 or 2 you will get better mileage acording to the brosure.

Its not the programmer. It sounds as if something is wrong elsewhere. Try to change your fuel filter.Unit453 I have to disagree with you on this. withing just a few days I installed the Hypertech, added 5"exhaust, & 265 BFG's, my milage went from 10.5-11.5 towing down to 8.24 mpg. as soon as I removed the Hypertech my milage went up to 9.6 mpg. next I am going to replace the cat & see if that does anything.

Unit453 I have to disagree with you on this. withing just a few days I installed the Hypertech, added 5"exhaust, & 265 BFG's, my milage went from 10.5-11.5 towing down to 8.24 mpg. as soon as I removed the Hypertech my milage went up to 9.6 mpg. next I am going to replace the cat & see if that does anything.

hand calc'ed?

if you want better towing and mpg go with superchips
hypertech has better shifting and topend hp

hand calc'ed?yes I dont have the display.

My milage improved substantially at lvl 1 and 2. my first tank on 3 isn't valid since I had a couple of very cold mornings where I let it warm up while I brushed 4" of snow off it, and had to use 4wd to get up the street (talk about killing mpg!)

285's are 33 inches tall, in fact i think its nearer 32.85 or something around there. That will help your speedo and improve your DIC slightly, but that doesnt really matter anymore as the onboard computer is now useless for calculating MPG since you put the programmer on there. Try bumping your tire size up a little, or better yet, fill up, travel a known distance then fill up again and hand calculate - it seems a little strange that so many, including myself have noticed an improvement in MPG, and you arent......

the best way to messure the tire size is to have your truck on a flat surface and place a straight board on top of the tire and messure straight down to the ground. that will give you the most accurate reading.

now to the on board computer: if you reprogram the tire size to callibrate the speedo it will also callibrate the odameter. Thus the OBC is getting the correct info so it should also give you the propper AVG MPG .

btw. 305's are 33's and Not 285's .:exactly:

btw. 305's are 33's and Not 285's
UUHHHH.... my 285/70/17 cooper sst's are 33". In fact they are 33.165" @ 55 PSI.
Measuring from the top to ground will vary depending on ambient temps and tire pressure setting. For a true tire height use a piece of chalk and make a mark on the bottom edge of the tire and asphalt/concrete. Drive the truck foreward one rotation until the mark on the tire is back at the bottom position and mark the surface where the chalk mark meets. Measure the distance inbetween the two marks and divide by pi (3.14) :deal: .
My remmington mud brutes on my z were 315/75's and 34.45" tall not 35's.
Not all tires are the same height with the same ratio's. Most programmers will be close but it sometimes takes a little adjusting and a good gps to get it dead on....but what do I know.... I am just a dumb coonass :rolleyes: !

Good luck and by all means have fun.