Oxygen sensors in general

[Brooks Ellis <brooks@fortnet.org>]

   Sorry that this is not totally Quattro-related, but we were talking 
about different types of hydrocarbon combustion reactions in chemistry 
class today. Our teacher pointed out that gas companies added 'oxygen' to 
the gas to reduce carbon monoxide. Then, I began to explain to him the 
way that most modern cars have O2 sensors. He knew absolutly nothing 
about this, and I was having a hard time explaining it to him. I told him 
that 'there is an o2 sensor in the exhaust system of most modern cars, 
and the computer will adjust fuel/air ratios based on this reading', but 
he still didn't quite get it. It confused him even firther when I 
explained that the additive (MTBE) would work ok on older cars, but on 
newer cars, it would fool the O2 sensor to some degree, and make the car 
run rough, and in some cases, create more pollution.
   Anyway, he wanted me to find some text on the matter, so I thought I 
would ask people on the quattro list, tending to be more knowlageable 
than the average joe. I was wondering when O2 sensors got widespread 
acceptance - I assume about the time we switched from carberators (sp?) 
to Fuel injection..but I am not sure, nor do I know the exact dates.
I was also just looking for any general info on the subject, it doesn't 
matter too much if it doesn't go into too much depth, I just need to show 
the guy how it works, at least in laymans terms.

    (obligitory audi content...)
  When did Audi first use the O2 sensor? I would imagine a while ago - 
1980? 1982? way before?

   I get about 23-24 mixed highway/city miles per gallon.. I do like to 
hit the gas a lot, but that figure seems low - I talked w/ an Audi 
mechanic, and he said I should get ~28-30 mpg highway....Could my O2 
sensor be bad on this car? I don't think it has ever been replaced, it is 
at ~71k miles.

Thanks for any info,

Brooks