Very interesting research here richard. To everyone claiming how inaccurate these gauges are you need to realize it doesn't matter. I believe the gauges are fairly accurate because I have experience with a similar gauge, the fuel economy is determined off of ODBII by comparing the flow at the fuel injectors to the speed of the vehicle. Even if the gauge was reading that he was getting 100mpg it's not the accuracy that's important it's the change with different trailer. Because of the way the gauge calculates fuel consumption it's actually much more accurate in determining the % of change than doing it longhand. Again the actual MPG isn't important but improving economy by 15-20% is a very valuable discovery.