well, lately in my 96 gsr the mpg has raised. i am currently getting about 27 mpg with city driving. the weird thing is when i fill up the tank and unscrew the gas cap, i dont hear any pressure releasing. the other thing is my car is taking longer to turn over in the morning when i start my car. what would cause this? first thing i thought of was maybe i need a new fuel filter? the car has the original one on. but i just replaced my cap and rotor not too long ago. my plug wires could be replaced. what does it mean if i dont hear pressure when taking off the gas cap? what makes my car take longer to turn over and start? i know its a bit cold out, but it bugs me.