If I install Air Tabs & Solid Aero Hubcaps will I get 10 mpg

When I started towing a Smart Car my average mileage improved. It had no impact on my motorhome mileage and I stopped using the motorhome (at the time a 27 ft BT Cruiser) for sight seeing trips. More and more we parked the motorhome and drove the little car. After a year of some big trips I looked at motorhome miles and toad miles and the mpg for both. It was a year we went to the Olympics in Vancouver and Alaska so big miles on motorhome. My average mileage between the two was 28. If you factored in the miles of towing it went to 39. These numbers may be slightly different and memory may be off but motorhome was averaged at 8mpg and car at 45mpg. Bottom line is if you want to get your best mpg on motorhome view it as a house on wheels and not a large car. Find the shortest route and drive at a reasonable speed. Finally I don't want this to sound like obsession with mpg. It is to be fun so what if we spend a little extra on fuel. Put in 40 gallons at total of 72 bucks in Tucson yesterday.