Understand there are ways to improve fuel economy on the V8 NV3500 version so can anyone tell me what to buy to do this? Also, my owner's manual sez I can call up the avg MPG on the speedo screen by using the left side speedo screen knob. It does not come up... I do get the miles traveled and avg speed but not the avg mpg???? Why would this feature "AVG MPG" be in the owner's manual if it does not exist... what am I doing wrong? Was anybody else able to get this feature working? I love this feature on my Honda van and I was looking fwd to seeing it on the new van. Thanks, BuzGuy at Harveys Lake, PA