Is he instantaneous readout accurate enough to tell me really accurate numbers? At 55-60 I show 10.0 to 11.0, at 65-70 it shows 12.5 to 13.5 on flat level, no wind conditions. Are those really good readings or is there some other factor since the readings should go down with more speed. ISC 350/1050 now 435/1200 due to Banks kit. Newmar Dutch Star 41'.

Submitted by Mark Overholser on Tue, 2013-05-07 17:00


The "Instantaneous Fuel Economy" fluctuates quite rapidly. Using the Rolling MPG gives an Average of the "Instantaneous Fuel Economy", ( the Default is 300, which is a 60 Second Average ). If your Speed and Mileage are reporting Correctly, AS WELL AS the Gallons of Fuel consumed, then your Average MPG will be correct.. I do know of Customers with the ISB engines getting 12.2 MPG, on the Flat Level, no Wind...

I've seen it happen even with my ISL powered Dynasty... no perceptible wind on what seems to be 'the flat' ... the instantaneous MPG will vary up/down by 1 or 2.... My suspicion is that there are winds, just not big enough to "feel". Just think a 5 mph tailwind changes into a 5 mph headwind. At 60 mph road speed that makes a change of air speed from 55 mph to 65 mph. That's about a 40% increase in the forces of air friction (drag) on the face of your coach. Maybe you can feel that 5mph wind; most drivers will not IMHO... how about a 3 mph wind ... 57 to 63 mph air speed change results in over 20% increase in drag. The above is enough to account for a few mpg change "instantaneously"; changes in road surface may have an affect also.