I have achieved an actual speed of 172mph on 1-88 near Aurora Illinois. I couldn't believe it, but my GPS read out 172 which was what the speedo showed. The speedo is not real precise, but I know I was above 170. I have a 2005 SRT6 with 42,000 miles. I run about 108 in 1/4mile. Not bad for a stock car. Impressive.