For quite a while now, usually a couple of times a year, I go through and clean the contacts in my ignition system (especially right after gas prices spike).
I can feel a slight increase in performance and I'm sure my gas mileage goes up too.
I don't really go for those $$$ cleaners (not that I haven't tried them) but for the most part, I just use some stuff by MG Chem. called Super Contact Cleaner (very nasty stuff!).
Today while I was checking my oil I dripped some into my fuse box. So I got out the q-tips and the contact cleaner and cleaned the fuse contacts (about 15 minutes).. BTW My 1990 BMW has about 120,000 miles on it and it still looks and runs great.
Well, I just got back from the store and I was shocked at how much brighter my headlights, dashlights and dome light were! Even my radio was playing a bit louder and sounded clearer (ok,.. that last bit could've all been in my head).
Now I can only wonder if I can fit a stepped attenuator into my factory stock radio/cassette!