6Lpowerstroke

So i was wondering if anyone knew how to correct mileage for a speedometer that is off? i drove 957 miles according to my odometer that is on my speedo that is 15 off.on the low side. i used 57 gal of fuel which calc to close to 18. i dont have a problem with that for mileage but im pretty sure its not right. any help would be appreciated, oh and i love black smoke in 3rd gear. thanks for the help.

Nick

35" 05'

the best thing to do is to get on an interstate with milemarkers. for every mile see how off ur odo. is. mine is 1/10 a mile off per mile. so if i go 400 miles on my odo. its actually 440.

Ph4tty

Well at least thats better than getting inflated milage. Good tip though

6Lpowerstroke

thanks for the info but i was kinda looking for a quick way to calc since iwork on the road alot now and it doesnt get drove alot.

Ph4tty

For 15% low indicated miles

(indicated mileage * 1.15)/gallons
(957 * 1.15)/ 57
1100/57
19.3 mpg

6Lpowerstroke

Thanks for the the help Phatty. That is around what i thought but i wanted to be sure. not bad for a crew cab dually of that age and for the way i drive. did you use some sort of formula or something? Just wondering.

Thanks again
Nick

Ph4tty

The formula is miles/gallons. You said mileage reads 15% low so 1.15 is the same as 115% of indicated milage.

6Lpowerstroke

thanks nick

Timmay2

Well lets start here, what have you done to make the speedo not accurate?

6Lpowerstroke

nothin other than tire size really. and went for 3 speed auto to 5 spd manua o/d.

fschiola

If you're not really sure about how far you are off, you could check it with a GPS receiver.

Ph4tty

Or refer back to the helpful tip in post #2

Ph4tty

I just looked at your profile and wow
A cummins out of a case into a 88 chevy with a freighliner intercooler. Neat ol frankensteiner ya got there.