Actually if your racing with your girlfriend and your 0.5 secs slower, that means your girlfriend weighs about 500 lbs. Let me explain before you get all mad at me. Everybody knows that 100 lbs is good for about a 0.1 sec advantage or disadvantage (depending on if you had the weight or remove it) so running with your girlfriend will had about 2 tenths of a second and not half a second. There was probably another factor that made you go half a second faster than just your girlfriend getting out of the car. Not trying to be an ass but just to inform you. And to answer the other question, some times, when that track is very slippery, it helps having a passenger as this puts more weight on the front of the car where you would need traction (if your running a front wheel drive). I experienced this first hand with my old car. I use to run a b18b and a 92 hatch with a turbo kit on it and I use to run faster (on street tires) with a passenger than I did running alone because the power was making me spin all of first and second gear and with a passenger, I had better 60 foot times wich in turn helped my 1/4 mile times. The weight was affecting traction more than slowing me down but you need a good amount of power to compensate for the weight disadvantaqe.