>These are reason given by various MFR at the time most changed to aluminum
>
>1.  lighter
>2.  cheaper
>3.  forms easier
>4.  more corrosion resistant (with proper coolant)
>5.  conducts heat (for cooling) better
>6.  can be used in thinner gauges there making the same cooling power in a
>smaller package.

Also doesn't set-up electrolytic reaction with other aluminum
components eg engine.