Ok my wife just got an ls about a week ago now. she is telling me that she is getting bad gas miles out of the car telling me that her grand am gave her better gas mileage. i was like yeah right. so i took the car for the week filled it up and i had to do some running around, and sure enough it is getting shitty gas miles. i was able to only get like 250 out of a full tank. what should i change or check to get some better gas miles? the car is 100% stock. with my civic and it had a b16 in it and i was able to get at least 320 out of it.