The Lowdown on Unleaded

The Millennium Bug?

As you are all no doubt aware leaded petrol is set to come off our garage forecourts by the year 2000. While most members cars are not affected by the millennium bug (the only silicon likely to be in the stereo), the death of leaded will affect most of us.

Since lead levels in the atmosphere have been linked to child health problems, the withdrawal of unleaded is no bad thing, but it does mean that we will need to arm ourselves with some know-how on what to do post millennium.

Up until the year 2000, unless your car already runs on unleaded, the lead in petrol has done two things for your car. Firstly it raises the fuel’s octane rating which in turn prevents ‘pinging’ or ‘knocking’ caused by uncontrolled combustion. Secondly it provides a lubricant layer between the value seats and the valve rods within the engines cylinder heads. All cars built after 1989 have had to have been built to run on unleaded.

Without this lubricant layer the value seats (the exhaust value especially) are worn, and the resultant particles oxidise, harden and cause further friction. This is especially acute at high temperatures, such as motorway driving, and can result in a blown engine. Cars built to run on unleaded contain hardened valve seats that can tolerate these conditions, and unleaded fuel contains alternative anti knocking agents.

However, I am reliably informed, that Volkswagen engines have had hardened valve seats since as far back as 1973! Unleaded petrol has been an issue in the USA since then and it was the North American market that led VW to standardise on the ability to run on unleaded. Once again VW were ahead of the competition. This being the case you might think you can sit back and ignore the whole debate. However valve damage can still occur above 4,000 rpm (well above the standard small engines) when the cylinder heads get particularly hot. If you own a VW with a 1600cc or above engine and/or you do a lot of motorway driving you will still need to consider the issues.

When leaded petrol is withdrawn by January 1st there will be alternatives in place, but the details of each option need to be looked at to show which will suit you best. A small amount of 4-star (leaded) will be available to vintage car owners and the racing fraternity. If you do not fall into one of these groups read on.
4 star will be replaced from the autumn onwards by pumps containing Lead Replacement Petrol (LRP). LRP contains non lead additives to prevent knocking and help protect you engine’s valve seats. The fuel nozzle on LRP pumps will be shaped so that it will not fit modern unleaded tanks and is not suitable for unleaded cars.
As well as LRP garages will increasingly stock bottles of Anti Wear Additives (AWA) that you can add to a tank of unleaded fuel to protect your engine. However, it is not advised to add AWAs to Lead Replacement Petrol. Furthermore unleaded petrol may have a different octane rating than you standard 4 star, so your engine may need re-tuning to use the unleaded/ AWA combination.
There are also a number of Fuel Catalysts on the market designed to let older cars run unmodified on unleaded petrol, the most well know being the Broquet™ catalyst. These consists of a metal alloy catalyst that either sits as a device along the fuel line or as wire bound metal beads within the fuel tank. You may have heard of these catalysts here in Wheelspin before, some people have reservations yet others swear by their effectiveness. They do, however provide a low cost way of running your car on unleaded
But all of these alternatives are never as sure as going the whole hog, and getting your engine converted to unleaded. You can either have new hardened cylinder heads fitted to your engine, have your existing heads modified with new valve seats or just exchange your engine for a “green” unit.
Your garage will be able to advise you best, but expect to pay around £425 for a typical flat 4 air cooled engine conversion (this would include dismantling, modified heads, pistons and barrels and reassembling). Larger 6 cylinder engines will be more expensive.
If you don't mind taking your engine apart you can send off to have your cylinder heads re-machined with hardened valve seats for around £95 + VAT & carriage, or £138 + VAT & carriage for 6 cylinder engines. I have details of an engineering company who will undertake the work, so you can contact the club for details.
So there will be alternatives come the millennium, which one you go for is up to your preference and budget. Of course, you can have full piece of mind if your engine is fully converted, but otherwise you can drive on after 2000. But, as will any car of any age, keep good care of your engine and keep it running cool.