[Latitude 28]

Tim Wade, asked about his fuel usage without a working gauge over in the Newell Coach Owners group on FaceBook.  I thought it would be appropriate to publish my response here.
We are coach #525 and have a 275 gallon tank. We get 8.3 @ 65 mph towing a Honda CRV. Our tank is 27" tall so about 10 gallons of fuel per inch not counting the sump which is about four gallons.  The low level fuel switch (if it works) is 3" off the bottom of the tank (not the sump) thus when it goes off you have 30ish gallons usable fuel. The fuel pickup for the generator and Aqua Hot are about two inches off the bottom fuel tank and below the low fuel warning light....so they will quit working soon after the low level light comes on. The engine fuel pickup actually extends below the tank level into the sump 9about 1" off the bottom of the sump that you see from under the coach. So you have some really good indicators as to the end of the run for a tank of fuel. Oh, almost forgot. We allow about 12% of a tank fuel for generator and aqua hot usage which has worked out pretty close as to the way we operate.

[folivier]

Steve are you using VMSpc for your fuel range? I found in my '98 that it was pretty accurate, more so than the fuel gauge.
On fillup unless I'd been running the generator all day my VMSpc estimate was within 5 gallons of what the pump said.

[Latitude 28]

Forest,
Don't have the VMSpc yet....that one is on the list:-)  When we picked up the coach the fuel gauge was in-op.   While learning the systems....and still learning I used the Detroit dash computer and full tanks to calculate the fuel burns which worked out similar to your results.  Once I had the new tank built and put in a new sender unit I still consider the gauge as an advisory unit with the low level light as a known working level indicator.....I hope I will never see that one come on.