ASK THE MXPERTS: “WHAT HAPPENED TO LEADED GASOLINE?”
Most two-stroke motocross racers get their leaded gas from VP race fuel or 100 Low Lead airplane fuel. It should be noted that there is nothing low lead about airplane fuel.
“WHAT HAPPENED TO LEADED GASOLINE”
The gas station down the street used to sell leaded gasoline when I was a kid. They called it “high test leaded.” I ran that in my minicycle until it disappeared. What happened to leaded gasoline?
Way back in 1923, a General Motors’ engineer discovered that adding tetraethyl lead (TEL) to gasoline raised the octane number. Early automobiles had very basic ignition and electrical systems, and “knocking,” what motocrossers call “pinging,” was a very real issue. Thus, tetraethyl lead was added to America’s fuel supply as an anti-knock additive—with the added benefit of the lead cushioning the valve seats. The lead allowed for high compression and more power from automobile engines; however, lead is very toxic, and exposure to it leads to cardiovascular and immune system problems (remember the scare about kids in urban areas eating paint chips off their bedroom walls and getting lead poisoning?). The fact that tetraethyl lead was unhealthful was not a secret to the automobile or oil industry, and the engineer who invented leaded gasoline eventually suffered from lead poisoning himself. But, the danger to humans was not the reason leaded gasoline was banned in the United States. Instead, it was the danger that leaded fuel posed to the newfangled catalytic converters that were mandated in the Clean Air Act of 1970. Leaded fuel stopped catalytic converters from cleaning the pollutants that were emitted out of the exhaust pipes. Thus, by 1975, every car sold had a catalytic converter, hardened valve seats and a sticker inside the fuel door that stated “unleaded fuel only.”
Leaded fuel was still sold at gas stations to supply the aging fleet of non-catalytic converter cars until 1992 when California banned the sale of unleaded fuel for road-going automobiles. The rest of the nation followed suit in 1996. The move to unleaded fuel was hectic at first, as fears of valve-seat issues and pinging kept drivers of older vehicles on edge (and many had their cylinder heads modified for less compression); however, modern ignitions have all but eliminated the concerns.
Most modern four-stroke motorcycles are designed to be run on unleaded fuel, and history has proven that modern two-strokes will also work on unleaded fuel, but there is power to be found in the higher octane of leaded fuel when combined with high-compression ratios. Whether your two-stroke race engine needs leaded fuel depends on if it pings. If it pings, you can add octane booster or run race gas (or even a percentage of leaded race gas to unleaded pump gas) until the pinging stops. It is important to note that leaded gasoline is still sold in the United States today, but mostly as race gas, airplane fuel, and for marine and farm engines.