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Politics : Foreign Affairs Discussion Group -- Ignore unavailable to you. Want to Upgrade?

To: Ichy Smith who wrote (203163)	9/16/2006 2:19:47 PM
From: Maurice Winn	Respond to of 281500

That's not how oil works Ichy. <Todays engines run far cleaner, and so one would assume that it would be easier to recycle....> You get molecular damage as well as pollution of the oil. True, the gobs of carbon floating around in it are reduced, as combustion efficiency has improved, with aromatics limited, but the oxidation and cracking of the oil is still happening. The main reason re-refined oil isn't done as enthusiastically as it was is that it's uneconomic. It's uneconomic partly because new lubricant from known feedstocks is cheaper to get a guaranteed quality, and the quantity of used oil has shrivelled. In the good old days, people changed their oil every 1000 miles and cars burned lots of it and leaked a lot too. Combustion was dirty, so the oil got loaded up with carbon. Strain it through a sock and it was pretty much back to how it was. There was a LOT of used oil around, looking for somewhere to go. Fuel oil was cheap, but lubricants were expensive, so re-refining made sense economically. Now, the acids and oxidation products and gums and molecular muck has to be removed. Carbon and lumps of stuff isn't such an issue. That's more difficult [expensive]. As an extreme example, LPG [propane/butane] and CNG [methane] cars don't produce any carbon. The oil stays clean-looking. But it fills with acids and darkens as the oxidation processes burn it and polymerisation occurs. No carbon, but the goo still needs stripping out. My guess [with zero checking] is that the most economic use for used oil is as fuel oil. Or perhaps long-haul diesel vehicle blending. Or marine diesel use. Re-refining became uneconomic in New Zealand during my time. Mqurice