well, I'll be the first to say copper
because its cheap and it works fine
true, the old CuBrass and its old school non-heat condusive welding did make it fall well below Al, but today's tech makes them efficient and cheap...hence my CuBrass dual core del sol/auto ex rad that I love to death (for 1/4 the cost of a fluidyne it works just dandy on my daily driver)
