Look there are tons of variatons... driver is a main one. Another is where the tests are done at, weather, temperature, etc all plays a factor in how well one test goes for a car and another goes for another car. Also have you guys ever thought of this...Most magazine tests are done on cars the first year they come out. Well the ZTT came out in 1990 and the C5 came out in 1997. You think the C5 maybe had better griping, higher technology tires that were 7 years more advanced than the 1990's OEM Goodyears? There's something to think on when your complaining that the Z is .3 or .4 or whatever in the 1/4 mile.