Anyone know how to restore that luster, that it was when it was new. Or is cheaper to just buy a new one. I'm talking about the fenders on the trailer.

mothers aluminum polish and a powerball on a drill

A truck stop will have aluminum restorer. It works pretty well. If it's pitted and white from oxidization, Paint or replace.

flitz works great on diamond plate.

Going to second this one ...

that's what I did......takes time, be patient, just "KEEP WORKING IT", like the Mrs. says

Aluminum polish and a electric boat/auto polisher with wool polishing pad. It will make it like new.

Personally I just use regular boat or car wax it works just as good. The polisher is what does all the work.

Flitz and a powerball.

http://www.offshoreonly.com/forums/s...ighlight=Flitz

We just simply use 3M HD here at our shop. With enough work you can polish a terd. It's just messy. The guys that polish at my buddies Semi detail shop look like coal miners.