Originally Posted by buck454
...do you close off bedroom and keep that thermostat high or leave open and run both ACs ..or suffer with cab air?
I refuse to suffer. LOL
OK...FACT...my 5.5kw Onan's published fuel burn is .9 gph at full load. My AC runs about 1/2 load if both compressors are in use putting my expected fuel burn closer to .5 or .6 gph
I've read that dash air reduces mpg by 1/2 or more mpg. So, if I drive 60 miles (at 60 mph) at 8 mpg I will use 7.5 gal with the dash are on and 8 gal with the gen/coach AC running. That means I will burn an extra .66 gal. That is practically a wash except I am not suffering.
Now, consider this. If you are fighting head winds or hills you now see your MPG go down. Let's assume it is a bad day and you are now muddling along at the same 60 mph but now are burning at 6.5 mpg and 6.0 mpg with dash air. The gals burned respectively are 9.23 & 10.0 and the gen/ac saves about .77 gal in an hour. Now you save a little bit of fuel by using the gen and coach air and don't suffer.
Now, finally, if you hit hills you will not be bleeding any HP off the engine. You should save fuel by the buckets, have more HP available for the climb, and stay cool at the same time. Here is an example. 20 min climb at 45 mph (15 miles) burning 4.5 mpg with dash and 4.0 without dash air. That is 3.33 gal vs 3.75 gals used. Dash used an extra .42 gal while gen used about .2 gal.
Even if the dash air only costs about .25 mpg you are near break even in most flat land, easy driving situations but motoring along with a cool environment. Any headwinds and/or hills quickly closes that small gap. I would also suspect that the tranny will not kick down as often in rolling terrain.
Hey...it's a working theory.
CAVEAT...diesel operators may have different opinions on the affects of dash air. Your mileage may vary, see own's operator manual for more information, my theory comes with no warranty implied or otherwise and always drive safe.
Don, Sandee & GSD Zeus. Gardian Wings earned are GSDs Gunny (7/11/15) & Thor (5/5/15)
2006 DSDP 4320, Spartan MM IFS, 2013 CR-V, Blue Ox Avail, SMI AF1, Samsung 197R Refer.