Exactly Mike, but you probably weigh more than she does. I realize this why I cannot get as good MPG as my wife. She is only 100-lbs and drives alone, when I drive it is me+her = 200-lbs extra. Think its 1-2% less MPG per 100-lbs. So that is possible 2 MPG hit, just due to me driving.
You are correct. But it's my car, thus, I can kick out the girlfriend! Of course, it gets lonely in the dog house at night, but my point is well made. But to add something else, you'd be amazed how much junk you have sitting in the car, which is dead weight. I usually carry my golf clubs (25-30 pounds?). Some junk in the middle console. Coffee cup. First aid kit (but I won't remove that). Flares. At the moment, I left my 12 pack of soda in may car (I think that's 5 pounds). I used to carry the emergency starter (you know, that 30 or so pound remote battery). Etc. Mike