Hi All,

I am curious what everyone's opinion is relative to running air condiioning systems while on the road in my motorhome.

I have a 2007, 30 foot Class C Motorhome with a Ford 6.8 liter V-10 engine. I averaged just under 8 miles per gallon for the past year while usually running the chassis air conditioning system.

Would I be better off running the generator/coach air conditioning to improve mileage?


Thanks in advance,

Dave

We have been told by several RV service people that it is more efficient to run the roof air than running cab air. We run our roof air when the weather is really hot because sometimes the cab air does not keep us cool. Unfortunately just the roof air does not usually keep us cool either so we wind up running both. I don't think we have ever calculated the mpg when we do this. Don't think we really want to know??? I'm sure another member can give you more technical advice and statistics.

Hi DavyD,

How many miles on your RV? If it is less than 12,000 (20,000 k) you may be in for a pleasant surprise. Mileage may improve at that point.

Do you get better mileage with the dash air off?

I've not done accurate measurements--but on my first major trip mileage did not seem to be different from running with or without the AC on.

In my unit the dash air does little to cool the rest of the RV.

The roof air power by a generator will use fuel. Probably the end result would be more over all fuel consumption.

I can run my roof air from my engine alternator because of modifications I've made to the RV. If you wish to peruse them surf here:

http://freecampsites.net/forum/technology/page-1/

and click on "solar boondocking"

Thanks for the reply Don. I have just under 10,000 miles on my motorhome. It will be interesing to see what happens after 12,000 miles. I believe I do better with the dash air off but I have not measured it for very long yet. I'm not really hung up on mileage but a 8 miles per gallon, a 10% improvement is a big deal.

Thanks again,

Dave

We have found that the generator works better for us! Good luck!

We run the dash A/C about all the time, If it is hot we run the roof air as well. We have used two roof units in the wild west to keep down the heat. Generator runs on diesel and takes 3/4 gal per hour under 75% load. This small amount of fuel pulled from our 150 gal. fuel tank would be hard to see. We get 8.5 -10 MPG on the road with A/C on or off.

We have that same engine in our 35' class A. We only use the generator and roof a/c when it is too hot for the dash air to keep the cab area comfortable. We also do see a noticeable decrease in fuel efficiency but not a large one.

Generally, you will loose a little in mileage by using your dash air but with a class C it is going to be much more efficient in cooling the cab area than would be the roof air. I have found that our genset burns very close to 1/2 gallon of fuel per hour when using one air conditioner. At 8 mpg, if you travel at 56mph you wold be burning about 7 gallons of fuel in an hour so that would make it now 7.5 gallons per hour and that also means just under 7.5mpg. Thus it would cost you about .5mpg to use the genset and the roof air.

Probably the actual change would be a little less, if you gain a bit from turning off the dash a/c but I suspect that to figure a cost of 1/2 mpg would be pretty close.