comparing mpg's is very difficult, to many variables. I live in the San Jose, CA area spend a huge part of my driving time sitting at stop lights, plays hell on mileage. freeways ditto. a 52 gal tank in my 08 ram 5500 @ 5bucks a gal makes it difficult to do comparisons. in my 03 3500 ad 05 3500 4x4 the milage seemed fairly accurate. You have tofill the tank exactly the same way each time, the gas station pumps have to be extremely accurate and if you travel alot you know they aren't so I figure one mpg one way or the other is as good as it gets.

 

Mine was showing about .5 mpg higher than actual. Once I installed my 285s without getting the speedo recal'd it is almost dead-on....

 

with the cruise control on, set at 55 mph, my overhead will display 27 mpg, sometimes as high as 31 mpg when there's a slight tail wind. I used to get all excited about that, but now I believe it to be "wild optimism" by the truck's ECM. I do have the taller tires and a Smarty, both of which seemed to made a difference in highway MPG.

Like a previous poster said, it's fun for laughs when other people look at athe overhead display and see impossibly high fuel economy on it

 

Yes but if you put bigger tires on then stock your odometer would also be out of whack so really the trip overhead is still off isn't it?

I had a friend with a Blackeberry that had a built in GPS in the truck and used my BD to adust the tires size so my speedometer/odometer is right, my overhead is still off though.

 

Mine will read 21 to 22 mpg, and when I hand calc it, I get 18 to 19 mpg. Truck is 100% stock.

 

Originally 5 years ago indicated 2mpg less than calculated. No telling what it is now.

MikeyB

 

My OHD has always been 2.5mpg optimistic but the odometer is only 100~150 yds off after 5 miles according to the odo check signs along the freeway.

 

Mine has been consitently 1.5-2mpg higher.. says like 21 and I am at 18-19...although I just filled up at 20.4 mpg yesterday coming home from Silver Lake...Had a 15MPH tail wind...lol but I will take it..

 

my overhead is normally 1-2 mpg high. The different reading from others (aside from driving habits and modifications) may be when the overhead is reset. I reset the overhead at every fillup. FYI

 

Mine consistently reads 9% high. Dead stock truck besides exhaust.

 

Mine is off by 4 mpg, it is nice to se it at 26 mpg

 

My Tom-Tom GPS says that my speedo is off. At 73mph on the speedo, the GPS says I'm doing 70mph. So +/-5% is being calculated into the fuel reading. 17mpg should be in the low 16's.
Don't know how true this is as I don't hand calculate (pump shuts off at $75) but I don't see how that overhead reading could be accurate.
Also looks as if my 36k warranty is only a 34200 warranty.

 

Mine is always off by 4.6 mpg on the high side speedo is dead on by my gps and mileage is hand calculated.

 

Mine is usually about 2mpg optimistic.

My wifes '07 Tahoe is within .1-.2 over 32,xxx miles. I check her mileage every other tank,and her average mpg is extremely close to actual hand calculated.

 

With my speedo being 100% accurate verified by Maggie Magellan, my overhead is usually 1.4-1.8MPG optimistic.

On a funny side note, I always thought my old '01 got terrible mileage because the EVIC stayed around the 13-14MPG range and I figured it to be optimistic like any other. I always wondered why it got such terrible mileage yet ran so good but never hand calculated it until recently. I finally got around to hand calculating a tank and got 19.1MPG out of it w/336000 miles on the odometer. Apparently, the overhead in that truck is about 5-6MPG PESSIMISTIC. First time I have seen or heard of an overhead telling anyone they are getting WORSE mileage than the hand calculation...