I really wish I had a magic RV that got the mpg that some claim. 26,000 miles with every tank logged. My best tanks were mid 7mpg, but my average overall is 6.374. This takes into account all the not really full and the tailwinds, towing and not towing. Now I am not saying that mpg in excess of 8 is not possible, but I've not seen it and I have tried just about everything. No to, 55-60, 60-65, 65+ warm weather, cold weather. About the only thing I have seen make a real difference is the few times I got 'REAL' gas w/o Ethanol,