Community Forums

DoggieDaddy · 03-01-2015, 04:57 PM

Since I started using the "econo mode" religiously the average MPG in the dash has ticked up and tenth of a mile to 7.0.

xtechgeek · 03-01-2015, 06:25 PM

Quote:

Originally Posted by MRUSA14

It isn't just about engine temperature, it's the fuel at the pump. When cold, a gallon of fuel weighs more and it is the weight of the fuel that determines how much energy it has which affects your fuel mileage. Conversely, warm fuel is less dense and weighs less, hence gives you less energy and MPG.

To maximize economy, buy all your fuel in winter!

Looks like the engine temp is more related to aerodynamic drag increasing due to winter air. I found a good reference here from Cummins: https://www.nptc.org/index.php?optio...419&Itemid=527

Also, looks like energy content of diesel only increases ~1% per 22 deg F change in temperature. If summer fuel is pumped out of the ground at 70F and in the winter at 30F (I think a stretch), this would result in a ~2% change in energy content per gallon; a small .14 mpg if averaging 7 mpg. Probably not great enough to overcome the increased aerodynamic drag or the decrease in energy due to B20 fuel. Fuel Temperature Compensation

Ann n Gene · 03-01-2015, 07:22 PM

But there IS a difference in summer blend diesel and winter blend. In winter there is more no 1 in the blend and in summer it is straight no.2 which is a little heavier and has more energy per unit thus giving better MPG than winter blend. Just my experience and JMHO 🚌🚗

Clayobx · 03-01-2015, 09:43 PM

Chuck, after 18,000 plus on my 2012 450 ISL it has settled in at 7.1 +/- a tad. It was in the low 6's breaking in. That 7.1 is at what I determine the sweet spot for my coach cruising at 62 to 63 mph at 1800 rpm's. That speed is concurrent with the GPS mph so the speedo is just about right smack on. No genny, no Agua hot but dash AC. Of course it goes down with the appliances added to your calculations. So 7 it is! Im probably a bit heavier as I'm fully loaded, water, gear, full timer stuff. FWIW engine and tranny temp with the toad in hot summertime temps range about 200* to 204* max.

CampDaven · 03-01-2015, 09:53 PM

Quote:

Originally Posted by Clayobx

Chuck, after 18,000 plus on my 2012 450 ISL it has settled in at 7.1 +/- a tad. It was in the low 6's breaking in. That 7.1 is at what I determine the sweet spot for my coach cruising at 62 to 63 mph at 1800 rpm's. That speed is concurrent with the GPS mph so the speedo is just about right smack on. No genny, no Agua hot but dash AC. Of course it goes down with the appliances added to your calculations. So 7 it is! Im probably a bit heavier as I'm fully loaded, water, gear, full timer stuff. FWIW engine and tranny temp with the toad in hot summertime temps range about 200* to 204* max.

Hi Clay!
Ditto for my 42' 425 and toad, same speeds.

brobox · 03-02-2015, 03:58 AM

It looks like the 3 of us are going to have a Cummins at the lower end of the millage scale. My last Cummins was the same way 7.3 MPG for a 350 when everyone else with the same modle MH was 8-9 MPG.

I took that one to Cummins and had it put on the computer......they showed me in the book....national average for the ISC in MH use 7.3 MPG. If I get into the 7's with this one, I think it will be as good as it gets from past experience.

Still not a bad deal from Cummins, had my engine computer and millage checked, software updated and they showed me in the book my millage was average....$99.

CampDaven · 03-02-2015, 08:24 AM

Just average Joes, Riding the Rainbow, having way too much fun.
Ho-hum.
But we ain't bored!

Diesel Diva · 03-05-2015, 10:12 PM

We've averaged 7.2 since purchase and over the past 17k miles we've traveled. Have not been tracking it manually but that's probably a really good idea. We don't trust the fuel gauge reading since we can't get more than 30 gals in when the fuel gauge shows 1/2 full. Entegra will check the reading while we are in Middlebury next week.

brobox · 03-06-2015, 04:23 AM

Quote:

Originally Posted by Diesel Diva

We've averaged 7.2 since purchase and over the past 17k miles we've traveled. Have not been tracking it manually but that's probably a really good idea. We don't trust the fuel gauge reading since we can't get more than 30 gals in when the fuel gauge shows 1/2 full. Entegra will check the reading while we are in Middlebury next week.

Thanks for that report....I haven't had problems fulling the tank....only keeping it in there.

Sorry you are having the go to Middlebury this time of year....not as much fun as the Spring.

joeplazek · 03-06-2015, 05:17 AM

Instead of rewriting this post and boring everyone one to death read my post of a few years ago and just remember that problems can be factory related and you yourself may have to be the "doctor". My fuel mileage problem is fixed thanks to this forum and countless hours searching.

http://www.irv2.com/forums/f258/side...es-164056.html