Models: all, Years: all

You have one of the above labels on your ex-Swiss-Army truck. What do they tell you and whats the story behind them?
The left label says that the truck has to be run on unleaded fuel, the right one that you have to run it with leaded fuel (or lead substitutes).

In 2000 the Swiss Army discontinued the leaded fuel for all their vehicles which naturally affected the Pinzgauers. They had to be converted to unleaded fuel. Intense research revealed that the conversion was done in a funny way, they simply changed the labels! The reason they decided for this was simple. The expected usage time until the truck will be sold is short and enough lead would have been build-up on the valves from previous use of leaded fuel to make them run for the expected timeframe.

In the past lead was added to cushion the valves and to lubricate the piston rings. After unleaded fuel was requested by law engines were build with hardened and different shape valve seats to be able to run with unleaded fuel. Running an engine without hardened valve seats without lead or lead substitutes will cause long term damage to the valves and seats leading to blow-by and finally failure of the valves and quite often to piston failures too.

If you want to avoid problems with your engine it would be wise to use a lead substitute at least every other tank. There were runors that the additive could ruin the lining in the tank but the information we gathered is that this is close to impossible. If the pink stuff peels off it is aging and/or mechanical damage and not an additive. The lining can't even be disolved with M.E.K which usually attacks everything.

Additional information:
As higher the engine RPM and load as more critical it is for the valves and piston rings if no lead or lead substitute is used. Long highway trips will faster lead to damages then slow trips where you just crawl along. For this reason an engine can live forever without an additive if it is almost exclusively used offroad.