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I really have my pulse on the issue, not less in Europe than over here in the States. Jean is right when saying that gasoline has been robbed of its lead contents gradually. And then, overnight, so to speak, there was no leaded gasoline available anymore, at least not here in California, and all my buddies with HiPo cars-where storming the gas stations that sell 100 octane race gas for $3.00 a gallon.
Europeans, foremost the analytical Germans who nowadays question everything without scientific proof, were afraid something like that could happen to them too and therefore wanted to know exactly what happens to valve seats when they are exposed to unleaded gasoline over an extended period of time.
Theoretically, as we all know, they will eventually be "eaten up" without the protecting lead found in leaded gasolines. However, the German car magazine "Markt," focused on classic cars only, took five different cars, among them a Volvo P544, and had them use exclusively unleaded gasoline for 40K kilometers. Before the test started, the heads were taken off an inspected and measured. After the test, they did exactly the same and guess what: There was hardly any regression measurable except on the Mercedes 230S they used as the fifth car!
Now, that might surprise many people; it sure surprised me as someone who helped developing fuels, but that's exactly the results of a real-live test. Apparently, many vehicles, among them vintage Volvos, will have no trouble surviving unleaded gasoline without hardened valve seats for a much longer time than generally assumed. Consequently, my advice to people asking me in this regard is to use some lead substitute once a while and do the valve seats when the head has to come off anyway or when they experience problems. Since that might not happen before the turn of the millenium, maybe even much later, I personally do not think that preventive measurements make a lot of sense, from a financial point of view.
Bernard
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