AMSOIL Metric 15W-50 Synthetic Motorcycle OilA reader asks: I’ve got a Ducati Monster 1200. AMSOIL Metric 15W-50 Synthetic Motorcycle Oil is suggested for this model. This engine revs up to over 9000 rpm, so it needs oil with good wear protection and foaming resistance. What is the zinc and phosphorus content of this oil? I can’t find this information anywhere.

Our answer: The fixation on zinc and phosphorus content in motorcycle oil is old thinking. With today’s ashless additive technology, zinc and phosphorus levels are far less relevant for some motor oils. Let us explain.

AMSOIL Metric 15W-50 carries the JASO MA2 and API SM specifications. The JASO MA2 oil standard signifies that a motorcycle oil is safe for catalytic converters. High levels of traditional motor oil additives like zinc and phosphorus can damage catalytic converters. Therefore, alternate technology has to be employed in order for the oil to provide adequate wear protection.

Metric 15W-50 Synthetic Motorcycle Oil employs the latest “ashless” additive technology. Therefore, it has less zinc and phosphorus than some of AMSOIL’s more traditional motorcycle oil formulas.

Why Zinc And Phosphorus Numbers Are Not Important Anymore

Let’s compare the zinc and phosphorus content of AMSOIL V-Twin Synthetic 20W-50 and AMSOIL Metric Synthetic 15W-50. The V-Twin 20W-50 has a more traditional formulation than Metric 15W-50.

  • AMSOIL Metric 15W-50- Zinc- 841 ppm, Phosphorus- 767 ppm
  • AMSOIL V-Twin 20W-50- Zinc- 1300 ppm, Phosphorus- 1100 ppm

Based on these numbers, is the V-Twin 20W-50 vastly superior to Metric 15W-50? Not at all! AMSOIL Technical Services tells us that the wear control between the two products is identical. They also tell us that ashless additives bring other advantages.

For instance, when there is blow-by, old-style heavy-metal additives (such as zinc and phosphorus) from can create engine deposits. Ashless additives do not create these deposits.


Ashless motor oil additive technology has revolutionized motor oils in the passenger car and heavy-duty diesel engine oil segments. This technology is also a major player in part of the motorcycle oil market. Simply looking for the motorcycle oil with the highest zinc and phosphorus numbers won’t automatically point to the best product.