First, an aside on the difference between quick and fast. A quick vehicle is one with a low 0-60 mph time, like the Tesla Model S P100D's claimed 2.5 seconds. A fast vehicle is one with a high top speed, like the 258 mph Bugatti Veyron 16.4 Super Sport. The Veyron, with a 0-60 mph time of 2.5 seconds, is also a quick car, but the two metrics don't necessarily go hand in hand.
In the real world, acceleration is usually done when merging onto a highway or passing someone in the next lane. Neither situation has anything to do with how quickly a car will move from a complete stop. Another part of the problem with 0-60 times is the inconsistencies and inaccuracies that come with manufacturer claims. Tesla, when announcing its Model S P100D, claimed to make the quickest production car on the planet. That led to a debate about what defines a production vehicle. The Ferrari LaFerrari and the Porsche 918 both put down equal 0-60 times, but Tesla claims they don't count because they're low-volume specialty vehicles. Does Tesla have a point? Maybe. Does it really matter? No.
Manufacturer claims can be all over the place. Some are conservative while others flat out lie. Companies will make up all sorts of rules and pseudo-comparisons in order to look good. And they often game the test conditions to pad the stats. This is why independent testing and reporting, like that done by magazines and websites, is so important.
But even then, there are discrepancies. Ever wondered why the 0-60 mph time from publication A is lower than the one from publication B? It's generally not because one has better drivers than the other, especially in today's world of launch control and automatic transmissions. Nor is it due to equipment accuracy, as everyone uses Racelogic VBOX data loggers. The time difference is usually due to the liberal use of a correction factor and the needless application of rollout.
A common practice is to cut the first 3 mph from a run, cutting as much as 0.3 seconds off the time.
Rollout comes from the drag strip. When you start a quarter-mile run, the timing lights don't start until the front wheel is all the way over the starting line. That number used to be approximated by subtracting the first foot of an acceleration run. Now a common substitute is to cut the first 3 mph from a run, cutting as much as 0.3 seconds off the time. Some publications post a 0-60 mph with rollout and others do not. Once again, there is no standard. In either case, it means the number in print isn't the number you feel.
Weather corrections need to be applied because engines make different power in different weather conditions. Temperature, altitude, and humidity all make a difference. While most publications claim to use an SAE standard to correct for weather variations during testing, the application of the correction changes from publication to publication. In order for a number to be comparable, it needs to be corrected. But weather corrections normalize for perfect testing conditions where an engine will be at an optimal operating condition. In the real world, a vehicle will almost never be driven in perfect weather, meaning it will never actually make the power the tests correct for.
In addition, not all publications correct for turbocharged engines. That can lead to quicker times for those that do, giving the false impression that they're somehow better or more professional because they have better stats. Modern turbocharging systems optimize their own atmosphere up to a point, so some publications feel there is no reason to correct. In the end it just leads to confusion.
Aside from weather correction and rollout, there are plenty of other factors that can change a 0-60 time. Non-standard tires, fuel, and weight can all affect performance testing. Some vehicles with sophisticated launch control systems that are set up for a perfect 0-60 run are actually slower in a rolling 5-60 mph test. Often times, test drivers will use and abuse a vehicle in a way no real owner ever would. Sure, it may put down a faster time, but most owners aren't going to subject their cars to constant 4,500-rpm all-wheel-drive clutch dumps with no-lift shifts.
Chevy geared the ZL1 just so you don't have to shift on a sacred 0-60 mph test.
Chevrolet says that the new ZL1 will hit 60 mph in first gear. So what. They geared it that way just so you don't have to shift on a sacred 0-60 mph test. The Camaro isn't even the first GM car to do this. Dodge built the Viper to hit 60 mph in first. Ford did the same thing with the Shelby GT500. They set the cars up just to do well on a single test. Would they drive better with a shorter gearing? Maybe, but then that 0-60 time may rise because a driver would have to shift.
As technology keeps improving and vehicles get more powerful and sophisticated, 0-60 mph times will continue to drop and everyone from enthusiasts to manufacturers will continue to tout the number as somehow more special and important than every other vehicle testing metric. Really though, the test has little bearing on what a vehicle will do if an owner decides to find a quiet, straight road and set a time of their own. So next time you see a claim, or even a real test, showing a 0-60 mph time is 0.2 seconds quicker than some other car, realize that doesn't make the quicker car better by default, and it might not be quicker in real life.