Oddly enough accelerating like that isn't always "legal". Where I'm from it could be classed as dangerous driving, and I believe in the USA it could fall under

Oddly enough accelerating like that isn't always "legal". Where I'm from it could be classed as dangerous driving, and I believe in the USA it could fall under "Exhibition of Speed". By and large it is more efficient to accelerate at full power, assuming your goal is to reach a certain top speed regardless, so if you were _really_ concerned about conserving petrol then you should be going full blast off the line. That said I expect the fuel usage such a situation to be negligible anyway, especially to someone who can afford/justify a car that does it in 4 seconds. My car isn't that fast, or particularly economical, but I know I've never thought "I'd love to accelerate at full power here to show how fast my car is, but I just can't justify the pennies it will cost me"! Outside of hyper-milers I wonder how many people do actually think about it.