Now I just HAVE to weigh in on this topic.
I have been driving the SAME VW for over 30 years, I have owned old Holdens and 3 LPG powered vehicles (including my wife's current vehicle), and have studied fuels for many years.
The USA has had unleaded fuels for more than 15 years and do not have LRP - all their VWs have to run on unleaded or stay in the garage! That's ALL aircooled VWs, including the pre-65 engine with "softer" valve seats (read on).
We lost Lead in fuels 2-3 years ago and many VWs here (including mine) have run on unleaded since that time with no ill effects.
The UK has just lost lead in their fuels and a lot of VW owner's are jumpy because they are getting mixed messages about the leaded/unleaded issue.
Here's a a brief ouline of what I know about fuels and the VW engine:
1. Tetra Ethyl Lead (TEL) in fuels did three things - increased the octane number, provided protection against Valve Seat Recession (VSR) and provided some lubrication to valve stems.
2. The VW engine does NOT need lead in fuel, for any of the reasons above - it has hardened valve seats (even the early bugs less hard seats are still HARD), the bronze alloy valve guides don't need TEL lubrication, and the octane requirement is met with normal unleaded petrol (91 RON Octane).
3. LRP is similar to PULP but has (in Australia) an additive called Methylcyclopentadienyl Manganese Tricarbonyl (MMT). This replaced the VSR protection that TEL used to provide. But it's not as effective, and it has less of a residual effect compared to TEL (Source: - BP and Shell Technical Advisory Service), so if your engine NEEDS VSR protection, then you must use LRP all the time. Only cars with "soft" cast iron heads need VSR protection - the VW engine does NOT need LRP. Because the VW engine runs hotter than it's water cooled cousins, it causes the MMT in LRP to foul plugs, causing hard starting and rough running. DON'T use LRP in an aircooled VW engine.
4. Oxygenates in fuels cause problems for carburetted cars. Adding Ethanol or Methyl Tertiary Butyl Ether (MTBE) to petrol reduces the amount of "fuel" in the fuel, since they contain used oxygen, but in small quanities, they can have a beneficial effect on the envionment and help raise the octane number of the fuel (Ethanol is about 129 RON octane and MTBE is about 116 RON octane). Modern computer equiped cars cope with these fuels by richening the mixture on the run, but aircooled VWs which HAVE to run on these fuels will need a larger main jet, otherwise the engine will run lean and hot. E10 (10% ethanol) petrol is available in the eastern states, and some stations around Sydney have been adding up to 20% ethanol to petrol and not telling the motorist - the VW engine will REALLY suffer if run on these fuels. WA and SA have no ehtanol in their fuels - it's outlawed. Woolworths PetrolPlus fuel contains up to 7% MTBE. WA and SA have outlawed the used of MTBE in their fuels.
Quote from the post above:
>ULP does require a CAT converter, (that's actually the Law. EPA) as it is more cancerous than LRP or even leaded fuel that's why CATs are required by law on new Vehicles and its a large fine if you are caught without one.
Oh please - it's the other way around. Catalytic converters were developed to help clean the exhaust of the worst pollutants, and it was found that lead in fuels quickly destroyed the CAT - coating the precious metals used (the actual catalyst), and rendering them useless - so THAT's why unleaded fuels were developed.
So it's not the law to use a CAT with unleaded fuels, but it's a requirement of CAT equiped cars that you DO use unleaded fuels otherwise you'll kill the CAT.
The problem is that the components in petrol with the highest natural octane numbers are the aromatic compounds like Benzine, Toluene and Meta-Xylene, but these are also the worst environmental components of petrol. So the first unleaded fuels needed more Benzine, compounds to replace the missing lead so that the octane number stayed high, but those same benzines were causing the most envionmental damage (they are carcenogenic).
The fuel companies these days are trying to reduce the amount of aromatics in petrol, but it's difficult to do so whilst keeping the octane number up to the required number.
PULP is a higher octane unleaded fuel - 95RON.
BP Ultimate, Shell Optimax and Mobil Synergy 8000 are even higher octane unleaded fuels - 98RON.
Just putting a higher octane fuel in your car will NOT make it go better - the octane number is just a number which describes the fuel's ability to resist detonation, and if your engine needs only 91 octane, it will not run better with 95 or 98 octane.
But if your current unleaded fuel has ethanol or MTBE in it and you switch to PULP or optimax for example, you might find an increase in performance, not because of the higher octane number, but because of the fuel composition - all hydrocarbons rather than being mixed with oxygenates for example. So you have to be very careful when talking about an engine's fuel requirements that you are not mixing apples with oranges.
There's a lot more about VW engine and fuel in my lengthy article at
http://www.geocities.com/aussiebug1970/octane1.html
[Edited on 28-2-2003 by aussiebug]