I happen to find an old piece of junk oil heater at the dump in the scrape pile and thought I would make an effort to save it
I cannot begin to tell anyone who rebuilds stoves how enjoyable, inexpensive and easy this hobby would be for you
I have about 4-5 hours total & $30.00 total into this beauty (including fuel, wick, etc.) and its like brand new and fully functioning once again!
I should have snapped some before pics to show you how awful this thing was, but anyways... here it is in all her glory (don't laugh to hard at the colors, this was just a fun test/trial and I had some left over gold stove paint from my 404 rebuild)
)! This was just a fun job, I will now know how much heat they throw and use 1200% next time. I know ill be doing some more of these (hardest part was fixing the gear that rolls the wick). everyone start keeping your eyes pealed for these old beauties 
) Its essentially a mini chimney with the draft flowing through the center of the fire that allows the flame at the point of "exposed" wick to burn very hot (thereby allowing that wick to absorb oil more rapidly as it burns) and almost with a "forced" or "induced" draft affect (like you see in a stoker grate with a blower forcing this air up through the grate and very intense heat in a very small defined area). The reason why these are called "smokeless" heaters is because of this forced draft effect it allows the the burner to preform at a very high heat, so high that it burns the fuel completely (or close to it) where as with an oil lamp you cant obtain this forced draft so much of the fuel is not completely burned (hence the black smoke floating up from the flame on an oil lamp).