Is my gas mileage what it should be?

-I have a 2006 Mitsubishi Eclipse GS, I decided that I wanted to see how many miles I could get on a single tank if I "babied" it, meaning no fast starts, no racing around, no speeding, stuff like that... I'm at half a tank with my trip odometer at 200 miles, which means 400 miles to a tank and my fuel capacity is 17.7 Gal ... is this as good as i can get it, or can I get even more out of my car and how? ......also, I have heard that it is okay to run the A/C high and it not effect gas mileage because of the newer technology, is that true?Converting your car to lpg gas is deffinately a good idea, with petrol at 拢1.37 now gas is deff a better plan. But you have been told wrong, gas uses just as much as petrol, so turn it off. Try to guess stopping so you don't use breaks and no speeding and get into 5th as soon as doing 25/30 mph. Also turn radio off and take all weight out of car including soar tyre if you can.