How accurate is the avg mileage on the dash?

[JWatkins]

Just curious about the dash report of avg mileage. It looks a bit optimistic to me, but thought I would check first.
Joe

[JWatkins]

Just curious about the dash report of avg mileage. It looks a bit optimistic to me, but thought I would check first.
Joe

[oemtech]

In my opinion, it's about as accurate as the "butt dyno". It only uses the last 50 miles or so I am told.

[Duner]

After 30K+ miles on my coach, I'd say on average (pun intended) it's about 0.5 mpg on the high side. Maybe even 1 mpg high at times. Sometimes pulling real steep hills, it goes bonkers and then reads very high, like 37.5 mpg. Maybe it just slipped a decimal point!

[FrontRangeRVer]

In my experience, it's optimistic by 0.5 - 1.0 mpg.

[JWatkins]

Well, figured as much. The old fill it and then figure your mileage is a bit chancy too because you rarely can fill it to the same point to be accurate. What is the best method, that doesn't cost $100 or more, to gauge the mjleage?
Joe

[paz]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Duner:
Sometimes pulling real steep hills, it goes bonkers and then reads very high, like 37.5 mpg. Maybe it just slipped a decimal point! </div></BLOCKQUOTE>
The data table for the computer that calculates mileage doesn't have data below 4 mpg. When the average mpg drops below 4, the computer starts over at 99.9. This quickly drops (especially if you are still climbing) so the 99.9 is hard to see. Unless you are watching very carefully, you probably won't even notice it until it gets down into the 30s or 40s. It will then eventually drop down to a more reasonable number.

[paz]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JWatkins:
Well, figured as much. The old fill it and then figure your mileage is a bit chancy too because you rarely can fill it to the same point to be accurate. What is the best method, that doesn't cost $100 or more, to gauge the mjleage?
Joe </div></BLOCKQUOTE>
The best method I have found to gauge mileage is to fill the tank and calculate your mileage, but this must be done over numerous fill-ups to average out differences in the way you fill the tank. As you say, you don't always fill the tank the same way or at the same gas station.

I use one of my trip odometers to record the mileage for my trip and the second trip odometer to record the miles driven on that tank of gas. I keep a pad of paper in the center console to record the mileages and gallons of fuel purchased. Every so often, I enter these into an Excel spreadsheet which I have set up to calculate mileage for each tank of fuel and overall total average fuel mileage.

[JWatkins]

Interesting the way that thing works. No MPG under 4???? Reset??? It's on a MH for crying out loud. It's probably not uncommon at all to go below 4 mpg pulling a grade.

Paz, that is surely the "tried and true" method that we have all employed for all time now! It is certainly the cheapest. I guess it is the only way that is under $100.00. I see that a scangaugeII is more toward $150.00. Of course, it has a bit more to offer than fuel mileage. What to do?
Joe

[Pueblo Dave]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JWatkins:
Just curious about the dash report of avg mileage. It looks a bit optimistic to me, but thought I would check first.
Joe </div></BLOCKQUOTE>
I've found it close enough to pen and paper to use as a dependable guide. Besides, your MH is going to get what it's going to get, and you're going to go where you're going to go, so unless you're going through some process to improve your mileage, what's the difference?

[JWatkins]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pueblo Dave:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JWatkins:
Just curious about the dash report of avg mileage. It looks a bit optimistic to me, but thought I would check first.
Joe </div></BLOCKQUOTE>
I've found it close enough to pen and paper to use as a dependable guide. Besides, your MH is going to get what it's going to get, and you're going to go where you're going to go, so unless you're going through some process to improve your mileage, what's the difference? </div></BLOCKQUOTE>
Ahhhh... the voice of reason. Thanks, I needed that!
Joe

[Clay L]

I check each tank with pencil and paper and keep a cumulative average as well (6.9 mpg for 33,000 miles).
I also use the ScanGauge and it's an average for the days travel so it's pretty close to the hand calculation.

As someone else mentioned a lot of things such as vehicle speed,grade,wind speed and wind direction affect the mpg so multiple tanks are necessary to get any meaningful information.
The ave mpg can be useful to show how your foot affects mpg though.

[Photog]

I keep track of milage in my log book. It does seem like the dash report runs about 1mpg above my actual.

[Fred and Bonnie]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JWatkins:
It's on a MH for crying out loud. It's probably not uncommon at all to go below 4 mpg pulling a grade. </div></BLOCKQUOTE>

Joe, this computer system was probably designed for GM P/U trucks, if one of them got 4MPG the owner would take it to be shot.

Fred