When I bought my latest R/T, it felt sluggish on the test drive which I attributed to it sitting on the lot for six months. Now after a few hundred miles, the best 0-60 times I can do is 7.1 sec. All my previous R/Ts were right around 5.2 sec. Granted, it's 100 degrees out and I'm still burning the original tank of gas which I'm sure was filled with regular instead of premium, but a full two seconds down? I'm no expert so any input?