How it's calculated

[yrralguthrie]

This is sort of a "I think" post. Just asking for comments.
Observing the miles per gallon indicator on the dash it changes easily. Since I have not reset the indication for several thousand miles the mpg indicated changes too much for the calculation to be total miles and total gallons used. So evidently it is calculating the mpg on the last few miles driven. Doing that it may be an accurate indication. This limited calculation is not going to include any stops and idles, which of course decreases the actual total mpg. I'm wondering why it was designed that way.

 

[HSKR R/T]

This is sort of a "I think" post. Just asking for comments.
Observing the miles per gallon indicator on the dash it changes easily. Since I have not reset the indication for several thousand miles the mpg indicated changes too much for the calculation to be total miles and total gallons used. So evidently it is calculating the mpg on the last few miles driven. Doing that it may be an accurate indication. This limited calculation is not going to include any stops and idles, which of course decreases the actual total mpg. I'm wondering why it was designed that way.

It definitely uses idle time in its calculations. Based on injector pulsewidth, and pretty much every engine sensor, as well and engine load and RPM

 

[yrralguthrie]

It definitely uses idle time in its calculations. Based on injector pulsewidth, and pretty much every engine sensor, as well and engine load and RPM

I am not trying to be a horse's butt, but where did you get this information? And a clarification on my part. I meant that the dash mpg indication is not using past idle time. Just that within a few minutes.

 

[DEG]

Doesn't really matter since it's not an accurate calculation anyway. Each fill up I reset the meter on the truck and use Fuelly to manually calculate the milage. The truck never reads the correct MPG not even one time. The truck always reads between .5 and 1.5 mpg better than what I actually got. My last two Rams did exactly the same thing; truck always read higher MPG than actual. I suspect it's an intentional design "flaw".

 

[Richard320]

Let us know if you ever crack the formula. I haven't been able to. How does it calculate mpg and range?

 

[HSKR R/T]

I am not trying to be a horse's butt, but where did you get this information? And a clarification on my part. I meant that the dash mpg indication is not using past idle time. Just that within a few minutes.

Depends on which page you are looking at on the gauge cluster.