Citing a doubling of aluminum prices over the last four years, the heads at Fuji Heavy Industries have decided to get a little heavier, declaring their intention discontinue the use of aluminum body panels on the Impreza, Legacy and Forester, replacing them with steel units as redesigned models roll out. Apparently, they've decided to leave the combination of all-wheel drive, ALUMINUM UND SHTEEL(!) to the purveyors of precision over at Audi.
I think only the hoods and trunk lids are made of aluminum. At least, thats what I have heard. If that were the case, switching to steel wont add that much weight.
And remember, steel is treated and manufactured differently then it was 10-15 years ago.
Plastic would be a nice idea. But I think a lot of companies stay away from it because it's a little more expensive to produce and it expands and contracts...leaving huge body gaps...just look at an Ion.