of leaded fuel for use in on-road vehicles in the United States. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum US$10,000 fine in the United States. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines. The ban on leaded gasoline led to thousands fewer tons of lead being released into the air by automobiles. Similar bans in other countries have resulted in sharply decreasing levels of lead in people's bloodstreams. A side effect of the lead additives was protection of the valve seats from erosion. Many classic cars' engines have needed modification to use lead-free fuels since leaded fuels became unavailable. However, "lead substitute" products are also produced and can sometimes be found at auto parts stores. Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion, and to allow easier starting in cold climates. In some parts of South America, Asia, and the Middle East, leaded gasoline is still in use. Leaded gasoline was phased out in sub-Saharan Africa, starting 1 January 2006. A growing number of countries have drawn up plans to ban leaded gasoline in the near future. Some experts speculate that leaded petrol was behind a global crime wave in the late 1980s and early 1990s. To avoid deposits of lead inside the engine, lead scavengers are added to the gasoline together with tetraethyllead. The most common ones are: Tricresyl phosphate 1,2-Dibromoethane 1,2-Dichloroethane MTBE As tetraethyllead use declined, industry had to decide how to make up the octane deficit between the principal marketable light fuels produced by their refineries, and the higher octane fuels needed for high-compression gasoline engines in the automobile fleet. Around 70% of the difference was accommodated by more advanced processes at the refinery stage, cracking other hydrocarbon products from the distillation stack to modify them into fuels that would blend gasoline closer the appropriate octane. Most of the rest of the octane deficit required chemical additives not derived from the refinery process. Tetraethyl lead was largely replaced in the US with methyl tert-butyl ether starting in 1979. MTBE is a toxic water pollutant, and a series of groundwater contamination scandals starting in the 90's prompted the EPA to begin phasing MTBE out in 2000. Ethanol MTBE's water pollution issues prompted plans for a phaseout, starting in