Just drive like a grandma, cost to stops when ever possable. I assume your hauling around lots of papers too adding more weight.. bad for Fuel efficiency great for carrying momentum... so coast as much as you can in neutral
look into a little 50cc or so sized scooter.. or a bike motor for a bicycle.. better than 125+ MPG they will do 30mph.. If i was doing a job like that that would be the way id do it except in the winter.. as I'm in Minnesota.. that would suck.
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