Danderson

If your running 3.15's and haven't had the tire recalibration done by the dealer,your overhead couldn't be expected to be accurate. I understand boxes do the same to them.

BigHornCTD

No, I think you need to heed your own advice on this one. In my 2006 owners manual:
Chapter 3: Understanding the Features of Your Vehicle
Section: Overhead Console with Compass/Temperature Mini-Trip Computer-if equipped
Page 136, first paragraph under the heading "Average Fuel Economy":

Shows the average fuel economy since the last reset. Average fuel economy is a running average of the amount of fuel used and the distance the vehicle has traveled.

So if you reset at every fill up, it will in fact be a per tank average.

P.J

No need for him to even try. What you mention is the end all of overhead accuracy arguments (always has been).

The overhead is for general reference, I believe that is why they got RID of the instant mileage, it was just TOO much of a joke to believe.

As far as getting those numbers on a low mile truck like that?? GREAT! I didn't start seeing over 14.75 until 3K miles. Now at about 4K miles I get 16.5 regularly with mixed driving.

P.J

Oh, and I just now changed out my OE oil. I wanted to do it at 3500, ended up doing it at 4030. No harm done, the owners manual says NOTHING but 7500, no "break in" change recommendations.

I wouldn't wait the whole 7500 the first time, but I can't imagine 3 to 5K is going to hurt anything.

duddin10

I have messed around with mine and have figured out that if you figure your mileage on where the pump kicks off when filling then the overhead is pretty close to that. If you top off your tank, as I do mine, then my overhead is over by 1.2- 1.5.

TurboTed

My brother's 03 was off by 2-6mpg, PERIOD. A lot of them are off, whether it was an average per fill, at the time or anything else. It was innacurate, and he never ran any box at the time. (He had an Edge EZ for a few months before he sold it, and the overhead was still off.) There are a lot of knowledgable people on here, and obviously the overheads are not always on.

DrDiesel

That`s absolutely correct.
The over head can not read fuel usage until the float inside the tank starts to drop.
So when you fill the tank and the fuel level is over the meters float level your fuel readings are off by that much.
My fuel gage takes 70 to 90 miles to move after filling the tank to the top of the filler neck . As I`m sure everyone has.

TurboTed

You are right. However, there are a lot of overhead readings that are innacurate on the trucks, just as there are a lot of Lift pumps that went, and go. We know how they work, and some of us are lucky that they work well. We know that if we drive in 4X4 or stop and go, or very fassssst, or step on it, the average readings per tank are less than if you drive a highway for 300miles at average highway speeds. BUTTT- some are not accurate.

DrDiesel

It`s not instantaneous. It`s accumulative. That`s why.

DrDiesel

Yeah. I know they are not a true linear gage/readout.
I just think that a lot of bashing by misinformed or misconceptions of a devise, it`s function or design intent is rampant. It`s just easier to trash something if you don`t understand it or don`t care to understand it.

TurboTed

Do 20% of us bash the lift pumps because we don't understand them?? I go on here to learn, not to bash. My son's liftpump on the 03 is still going.(50K miles). My brother hasn't had a lift pump go on 4 CTD's. Is that because we understand how liftpumps work, and others don't?? Yes there is some abuse, but not with the overhaed readouts. The overhead on the 03, and 05 is an average. I know that for sure. Other than that, perhaps I require more educating??

JWash1

Doc, would you please, for those of us that are not grasping your point of view, please define the words; Accumulative and Average and how they differ. My Owners Manual Says Average, You say Accumulative, but then you earlier said something about "the mileage at the time" which means "instantaneous". I am So Confused!

DrDiesel

Hmmmmmmmm. Sounds like your over head is off....
I never said instantaneous. You did...That`s why your confused...
It`s an average of fuel used to mile driven. It`s a basic logic module function/adaptation of fixed parameters that can be skewed by fuel filling over the meters limit of travel. This adds fuel that the meter can`t read and account for. Therefore your readings are not even close to a hand calculation.

DieselMachine

Wow, some people in this thread are making this topic way to complicated...its not hard to logicaly think about how the overhead works.... especialy when it states directly in the owners manual HOW the overhead works!

JWash1

Isn't that cute, a S.A. answer Definition Please. Thanks