Ok fellas maybe this is the place for my ambulace...lol

she is part van, part dually, and very heavy; 8180 pounds
460, automatic, dually, 16.5" wheels. lights,siren, i added my 1750 watt inverter. It still has all of the lights and relys for the inside, 2 control panels for that stuff. front and rear heat/AC. jump seat, a long bench seat with storage under both. It has a nice work bench in there (becasue it was converted to a rescue unit) to haul tools instead of people.
Backup alarm, high idle switch (awesome for those cold starts) for keepoing the rpms up a bit for keeping the alternator going when all of its power hungry features are running, and dual batteries so you dont need a jump when you run one dead... (unless you have it set to both)
Gas... yup, it uses a little. (though i was called a liar by some nice members in another forum here) it gets about 12 mpg highway, and 8-9 city.
I need all the shelves because I use it for my busness. I am a professional mobile sharpener. When that old fella tells you to pull the edge of the knife away from the stone.... I am the certified professional sharpener who can tell that guy he is wrong, and I have papers and a business to prove it.
anyway, like everyone else, i would like to milk as much as possbile from the gas tank.
Do you think an aod would hold up? I dont normally roll loaded anymore than about 9000 pounds total.
It is a non-catalyst vehicle, so no cats apply.
supposedly it has 64000 miles, and it runs great. I bought it directly from a fire dept that used it for a reacue unit. that town has a population of 2500 people, so I dont expect it to really have many miles on it.
it does drip a little oil.. about 1 quart in a month.
So, tell me what you think, and what you would recommend for a possbile imprevement in mileage. I know it will never reach my goal of 100 mpg, but i almost tend to think it could do better.
Vin is 1FDKE30l9EHA65049
Thanks Fella's