Answer the following question: Extract the answer to the question from the following context. Question: What material was once moved by the assistance of vacuum power in an automobile? Context: Manifold vacuum can be used to drive accessories on automobiles. The best-known application is the vacuum servo, used to provide power assistance for the brakes. Obsolete applications include vacuum-driven windscreen wipers and Autovac fuel pumps. Some aircraft instruments (Attitude Indicator (AI) and the Heading Indicator (HI)) are typically vacuum-powered, as protection against loss of all (electrically powered) instruments, since early aircraft often did not have electrical systems, and since there are two readily available sources of vacuum on a moving aircraftthe engine and an external venturi. Vacuum induction melting uses electromagnetic induction within a vacuum.
Answer:
fuel