Is this possible??

[drz400smoto]

So today I was trying to figure out highway mpg. Most of my driving was highway from full tank and I got down to about 3/4 tank when I got home so I topped her off to see how much fuel was used. My problem is im not sure how much my odometer is off with the 35's. I went past a sign with miles left to my destination looked at my odometer then looked at it about 30 miles later. Well the distance according to the signs was 33 miles and my odometer had only showed an increase in 26 miles. So I figured 33/26 is 1.27 so I can I multiply my truck odometer by 1.27 to get accurate milage? Because I thought my milage seemed too good to be true. Had 146 shown on the truck so that means 185.42 then divide that by 9.3 gallons it took to fill up. Results are 19.9 mpg. This was highway cruzing between 60 and 80 mph. What do you guys think? Sorry about the long post..

[sldghamr]

you should get your odometer/speedometer updated for the new tires.

[drz400smoto]

Originally Posted by sldghamr

you should get your odometer/speedometer updated for the new tires.

Yea I just can't justify spending $200 to know my accurate mpg.

[offroadit]

I found a calculator on the net that would tell you how much your speedo and odometer are off. My truck came with 265's and now I have 35's and it said it was 9.27% off.

[dhanna6powerstroke]

Originally Posted by drz400smoto

Yea I just can't justify spending $200 to know my accurate mpg.

Find out how many revolutions per mile your tires make. (Usually can get the info from where you bought the tires) Take it to ford and they can hook the scan tool to it and see if that RPM (revolutions per mile) is an option. If it is or thety have one that is close they can change it in the computer.

[999renville]

do the same calculation you did but use the actual mile markers on the side of the freeway. check mile marker to milemarker. the freeway signs saying 33miles to X are not as accurate. do several calculations 1 mile, 5 miles, 10 miles. average the results...your set.

[drz400smoto]

thanks guys I will try that

[landofconfusion]

If one were to get the dealorship to re-adjust revolutions per mile, would this be eliminated if one was to custom tune a truck from lets say SCT by either DJ or spartan IDP

[FordCowboy]

well that seems close. From what I have learned you have to figure this stuff out based on a percentage. So if you went a supposed 30 miles and you actually went 33 that is 10%. So that would mean a little less than your 19.9mpg. I sat down one day and actually figured out revolutions and distance traveled one time for my 97 with 35's and it came out to 12% difference. So then I just multiply my mileage and add 12%. I don't know exactly what to tell you because especially when you get into tire sizes like 35 they have a lot of tread depth so if your tire is full tread or half worn it can make a bit of a difference in your calculations.

[dhanna6powerstroke]

Originally Posted by landofconfusion

If one were to get the dealorship to re-adjust revolutions per mile, would this be eliminated if one was to custom tune a truck from lets say SCT by either DJ or spartan IDP

It should not be affected when installing a programmer unless there is an option to calibrate tire sizes and you use this option.