and the size of you tires, also the condition of the road. As far a speed shifting, I would keep it to a minimum. It's not worth the extra 0.10 seconds (to me anyway) compared to the wear on the synchros. Just something to think about when your Z reaches 100,000 miles or so. I'm not saying count 1 Mississippi between each shift, I'm just saying it's not a good idea to bang gears all day everyday. Enjoy the Z and welcome to this fantastic forum. You will learn quite a bit of info from this place.