The spark-Optimizer is a closed-loop type electronic control device that continuously corrects the ignition timing; in effect it re-tunes the engine some ten times every second. In contrast to the better known pre-programmed controls, the Optimizer is an adaptive type system, in which the output influences the input. By providing the correct spark timing all the time, the Optimizer reduces fuel consumption considerably.This paper describes the spark-Optimizer in its advanced version including recent improvements, like biasing. A comparison with other electronic spark control devices show its superiority in accuracy, flexibility, simplicity and production costs. Samples of test results show considerable fuel savings with the Optimizer.