Zinc is contained as part of the standard additive package in virtually every major brand of engine oil sold today, varying from a low volume of 0.10 per cent in brands such as Valvoline All Climate and Chevron l5W-50, to a high volume of 0.20 percent in brands such as Valvoline Race and Pennzoil GT Performance.

Organic zinc compounds are used as extreme pressure, anti-wear additives, and are therefore found in larger amounts in oils specifically blended for high-revving, turbocharged or racing applications. The zinc in your oil comes into play only when there is actual metal-to-metal con tact within your engine, which should never occur under normal operating conditions. However, if you race your bike, or occasionally play tag with the redline on the tach, the zinc is your last line of defense. Under extreme conditions, the zinc compounds react with the metal to prevent scuffing, particularly between cylinder bores and piston rings.

However - and this is the important part to remember - available research shows that more zinc does not give you more protection, it merely prolongs the protection if the rate of metal-to-metal contact is abnormally high or extended. So unless you plan on spending a couple of hours dragging your knee at Laguna Seca, adding extra zinc compounds to your oil is usually a waste. Also, keep in mind that high zinc content can lead to deposit formation on your valves, and spark plug fouling.

Among the products we found containing zinc dialkyldithiophosphate were Mechanics Brand Engine Tune Up, K Mart Super Oil Treatment, and STP Engine Treatment With XEP2. The only reason we can easily identify the additives with the new zinc compounds is that they are required to carry a Federally mandated warning label indicating they contain a hazardous substance. The zinc phosphate they contain is a known eye irritant, capable of inflicting severe harm if it comes in contact with your eyes. If you insist on using one of these products, please wear protective goggles and exercise extreme caution.

As we mentioned, organic zinc compounds are already found in virtually every major brand of oil, both automotive and motorcycle. However, in recent years the oil companies voluntarily reduced the amount of zinc content in most of their products after research indicated the zinc was responsible for premature deterioration and damage to catalytic converters. Obviously this situation would not affect 99 percent of all the motorcycles on the road - however, it could have been a factor with the newer BMW converter - equipped bikes.

Since the reduction in zinc content was implemented solely for the protection of catalytic converters, it is possible that some motorcycles might benefit from a slight increase in zinc content in their oils. This has been taken into account by at least one oil company, Spectro, which offers 0.02 to 0.03 percent more zinc compounds in its motorcycle oils than in its automotive oils.

Since Spectro (Golden 4 brand, in this case) is a synthetic blend lubricant designed for extended drain intervals, this increase seems to be wholly justified. Also, available research indicates that Spectro has, in this case, achieved a sensible balance for extended application without increasing the zinc content to the point that it is likely to cause spark plug fouling or present a threat to converter-equipped BMW models. It would appear that someone at Spectro did their homework.