4th gear is best. You said from highway speeds... and most of us have a slightly faster view on what that is than the average folk. Dropping to 3rd is slow becuase of the motion, and the syncro mesh is not going to want to let you slam it in there cleanly. Once there, you will be on the backside of the power band so you will get little gain, and immediatly have to go to 4th anyway. 4th has good pull, and will carry you for a while like the last guy said. But then again, it is your car. Drop straight to red line if you want.