I have used 3 different G-tech's , burrowed others than finally bought my own . They all have read the same in all cars , and 1/4 times where acurate and MPH was off at the track , but at the track they average the last 60 feet , so 60 feet before the finsh line there is a censor and at the end of the 1/4 theres a censor and they average those speeds together for 1/4 speed , Why I do not know . So that is why the G-tech differs a little . I love my G-tech , I have tested in cars ranging from 17 sec E.T."s to 12 sec E.T.'s I is also a good tuning tool, rather drive to track that is 50 miles away on a Saturday .
Thanks ,
Joe