Join Date: Feb 2007
Location: San Diego, CA, USA
If I was to guess, the reason for the shift to 50 weight oil for the Multistrada it would be the use of a catalytic converter.
Zinc Dialkyl Dithiophosphate (ZDDP) is a anti-wear additive to motor oils. ZDDP, however, contains phosphorous that has a life-shortening effect on the catalysts used in exhaust emission equipment, first only on cars, but now more recently on motorcycles. So the US Environmental Protection Agency mandated a reduction (from a maximum of 0.12% down to 0.10%) of anti-wear additives containing phosphorous in engine oils.
This EPA mandate may be the reason why the Ducati-recommended Shell oils are generally unavailable here in the US.
It's important to note that this mandated reduction was only required for the "energy conserving" designated lower viscosities. The higher viscosity oils were not required to meet this lowered phosphorus level.
Another reason, as Bonaventure points out above, is that shared sump motorcycle engines tend to sheer (thin out) the oil over time. The EPA has pressured engine manufacturers to extend oil change intervals to reduce the disposal problem of used motor oil. But therein lies a problem. Tests have shown that oil that also lubricates the gearbox in a motorcycle looses viscosity quite quickly. The gears in the transmission are the significant factor in cutting the longer oil molecules into shorter pieces that are less viscous.
In one series of tests, non-synthetic motorcycle-specific oils had lost over 30% of their viscosity at 800 miles, and over 35% at 1,500 miles. It should be noted that the viscosity of synthetic-based oils generally drops more slowly than that of petroleum-based oils in the same engine. This doesn't speak well for 7,500 mile oil change intervals (also encouraged by the EPA).
Starting out with a 50 weight oil means that it takes longer to end up with a 20 weight oil, for example.
Last edited by Shazaam; May 2nd, 2015 at 11:57 am.