I wouldn't jump to any conclusions at first. I would wait and test it at least another time or two before I determined it had a drop in mileage. I've had erratic mileage like, too. Basically, to get the average MPG, calculate the average of 3-4 tanks in a row, and also compare them to the others.

 

I get 25 or 26 mpg with my 5 speed infairly aggressivemixed city/cruising (commuting) driving since purchased new so don't consider the mileage you are getting to be "lousy". I would give it a few more tankfuls to get an average figure.

 

I just checked this last tank, and got 27.4 MPG. I guess I jumped the gun!
Anyway...I am going to make my own cold air intake and use a K&N filter, then check my plugs and go platinum split tip I think.
Thanks!!!

 

I just replaced my plugs with NGK ZFR5F-11, maybe use those if it's time? Seem to work super nice.

 

If you want to go platinum stay away from the bosch.... stick to NGK plugs in your car, the iridium's seem to work well as long as they aren't the pointed (cone like) electrode style...