Actually, aluminum tarnishes white when it oxidizes.
Aluminum, once it is polished, you can either hit it with some mothers cream polish
and a soft rag, like I do, or go the low maintenance route and buy some zoop seal after it has been polished, and never worry about it again.
Heat wouldn’t be affected. I can’t see how a fully polished pipe will make any appreciable differrence in heat/efficiency etc…
I have some more polishing to do this weekend, and I might get bored enough to polish the actual intercooler end tanks. I dunno, we will see…