I'm not sure how you judge bad gas mileage just on 200 miles per tank, are you running it to empty? I get about 280 but I run mine down to near empty so that when I refill it takes a full 15 gallons.
I usually set the trip meter to zero at each fillup, then when I fill up next time I note the gallons used to fill up, and divide the miles on the trip meter (reset it for next time) to get the MPG. I get 18 - 20.
__________________
|