Unleaded/Leaded: you did ask...

["Mark Battley" <m.battley@xxxxxxxxxx>]

I was going to stay out of this one, but John did ask again:   :-))

<What about the rumour that I quoted and which still concerns me that ULP
<contributes nasties (benzene ?) which a Cat removes but which a leaded
<vehicle WITHOUT CAT sends into the atmosphere?  Forget whether it damages
<the vehicle - what does it do to the rest of us?  This was the original
<rumour that was being pushed by the classic car lobby in Australia at one
<time and which I have heard elsewhere but never head resolved.

<One last time and then lets all drop it in favour of a drive in the
<mountains - does ULP require a catalytic converter to remove hazardous
<pollutants or is this another urban myth?

Not a myth, from what I've read from a range of sources. As I understand it
(I'm not a chemist), unleaded petrols generally use relatively high amounts
of aromatic compounds as one way of achieving the required octane levels
that used to be provided by the tetra-ethyl lead. Aromatics are particular
forms of hydrocarbons based on the CH ring of pure benzene, including
benzene itself, toluene, xylene etc.  These are relatively unfriendly
compounds: benzene is particularly nasty, a proven carcinogen, toluene is
not a proven carcinogen, but does bad things to the central nervous
system.... and when you burn it it tends to break down into benzene. There's
heaps of stuff on the web on the dangers of these chemicals. Supposedly
(http://www.nsc.org/ehc/ew/chems/toulene.htm) 92 percent of toluene
(produced) is used as a component of gasoline.  There's an interesting
article with particular reference to Australia at
http://www.peg.apc.org/~nexus/ulp2.html. Supposedly "50% of the benzene
emitted from the exhaust comes from the actual benzene in the fuel, 40% is
from the toluene (methyl benzene), and 10% from other aromatics in the
fuel". Catalytic converters (once they are warm..) do a good job of cleaning
these up. 

Some of the classic car lobby in NZ have tried to push this line with the NZ
government to get them to reintroduce leaded, but it's not going to happen.
NZ does not have compulsory catalytic converters so very few cars have
them.. yet all have to be run on unleaded.

And in response to a couple of Paul Irvine's comments:

<First of all my qualifications. I live in California therefore I have many
<years of experience with unleaded fuel. Now that the conversion is
happening
<in other countries I see the same type of hysteria and misinformation
<propagating there as it did here in the early 80's.

You are right, there is a lot of misinformation, from both sides. However I
believe that there are real issues of concern. As I understand it the USA
(California initially anyhow) had a phase out period for leaded, and
introduced compulsary catalytic converters... and has a relatively young car
fleet compared to many other countries. (Although we've got newer Alfas than
you, nah, nah, nah....) 

<The stories of old rubber fuel lines cracking and leaking, of valve seats
<and guides wearing out - they're all true. The fact is that old rubber fuel
<lines do eventually crack and leak and all valve guides and seats
eventually
<wear out. But if your government has just recently mandated the use of
<unleaded fuel then just about every occurrence of the above mentioned
<maladies will thereafter be blamed on the new fuel.

Fair comment: but there were definitely real problems (leaks, fires,
pinking) in NZ when the new fuels were introduced and leaded stopped being
sold. At the time the standard oil industry response was "but it was an old
and poorly maintained car..." but, hey, they used to run fine on the old
fuel! Higher levels of aromatics WILL and did accelerate the deterioration
of rubber (and other) fuel parts. In my case, a PO had "repaired" rust in
the top of the fuel tank with fibreglass patches (presumably polyester
resin). Not an uncommon approach, but probably could be called "poor
maintenance". First tank of the new fuel the patches literally fell off:
message for me at work that there was a huge pool of petrol under my car in
the carpark. Toluene makes a very good solvent for styrene based resins. I
replaced the fuel lines anyhow as a precaution: which you well might argue
should be done anyhow on a 25ish year old car.

Eventually it did come out that the first few shipments of the new unleaded
were very high toluene content (50+%?). Levels are lower now. I haven't had
a problem since I fixed the tank properly (brazing and POR15 coating). I'm
not worried about the valve seats, there is enough empirical data that they
should be okay.

<92 octane is still 92 octane weather it contains lead or not. The fact is 
<that using lead was the cheapest way for the oil companies to increase 
<the octane level of the fuel. Unleaded fuel of the same octane rating is 
<not going to cause pre-ignition problems.

Yes, but with the caveat that make sure you are comparing octane with
octane. In NZ the RON of the "super" unleaded is 96 as it was for the
leaded, but the MON and hence (RON+MON)/2 are less: which is why people had
pinking problems despite the octane "being the same". Not such an issue in
the USA where petrol is generally sold by (RON+MON)/2.

Mark Battley
Auckland, New Zealand.

1974 Alfa Romeo 2000 GTV
New improved model with new front suspension and some real metal (not that
oxided stuff) to bolt the front antiroll bar to: throw some paint at it in
the next few days and it's ready to drive, yippie! Don't you really hate
welding upside down while lying on the floor....

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