VTEC is a mix of being able to get more specific output from a smaller engine without sacrificing streetability and fuel mileage. Whether you use that fact to be able to get up to speed quicker on the on ramp going to work so that you can spend more time at cruise speed [which is where you get your best gas mileage], or spend 90% of your time in VTEC squeezing every last pony out of the engine doesn't really matter. In stock form, VTEC engines are sort of a compromise without compromises between performance and economy.