A variety of methods and arrangements for improving the fuel efficiency of internal combustion engines are described. Generally, an engine is controlled to operate in a skip fire variable displacement mode. Feedback control is used to dynamically determine the working cycles to be skipped to provide a desired engine output. In some embodiments a substantially optimized amount of air and fuel is delivered to the working chambers during active working cycles so that the fired working chambers can operate at efficiencies close to their optimal efficiency. In some embodiments, the appropriate firing pattern is determined at least in part using predictive adaptive control. By way of example, sigma delta controllers work well for this purpose. In some implementations, the feedback includes feedback indicative of at least one of actual and requested working cycle firings. In some embodiments, the appropriate firings are determined on a firing opportunity by firing opportunity basis. Additionally, in some embodiments, an indicia of the current rotational speed of the engine is used as a clock input for a controller used to selectively cause the skipped working cycles to be skipped.