ep3 bad mpg

Hi All,

I'm new to the forum and if this topic has been overdone, please direct me to the best thread.

I am the second owner of a 2004 si that is completely stock save for 17" rims. When I bought the car at 125k it got 26 mpg consistently. Now I am at 189k and within the last 2 months my mpg has dropped to 22-23. Driving habits and commute haven't changed. The car runs great and its service is always up to date. I fix anything and everything it needs. One oddity is that the original owner told me that he ran straight 30w oil. I've run the recommended 5w 20 since I purchased it and it does not burn any. My wife's current and previous ep3s (we've had 3) both got 29 mpg consistently as have several other owners who I have spoken to. She accelerates harder around town but drives slower on the highway (70, no cruise control). I drive a little easier around town but do about 80 on the highway almost always with cruise on. My mechanic, who has worked on all of the cars and has worked on hondas for 45 yrs has no idea except for the possibility of a vacuum leak that he found when he searched on a specialized mechanics software that he pays for. I love these cars! I would also love to figure this out. Any help would be appreciated. Thanks! Rob