I bought this car to commute to school (45 minutes away) cause people say civic gets good gas milage. It currently sit at 112K miles since i bought it at 108K 2 months ago. Anyway, I'm only getting 320 ish on a full tank? Shouldnt i be getting atleast 350 to a tank?

my brother's mustang gets better mileage to a tank on the high way then me .

 

Since youve gottan the car around a 100k. DId you or the previus owner do a 100k maintance on it? timing belt/ water pump? those arent likely issues of the bad gas mileage.

Try changing your spark plug and wires.
Fuel filter and air filter. Also run some injector cleaner in there.
WHen i had an EX motor in my car D16y8 i was pushin 440 to a tank with it.

 

accordin' to the dealer, they did a 100k maintance but now i'm thinkin' its BS!
well, i guessing i'll be doing maintanace this weekend. thanks for the help.

 

Sorry to be PITA about details, but "a full tank" to me means nothing and implies you run totally out of gas before refilling. The fuel guage is only a rough indicator and can vary quite a bit. The only way to describe fuel mileage is in miles/gallon. How many miles were driven, and how many gallons did you consume?