The reason for multi-grade oils is to allow you to turn your engine over on cold days. Ducati engines take a relatively long time before the oil reaches the rocker arms, so it would seem that an oil with a lower winter viscosity would be an advantage, certainly on a cold day start. Once the engine is up to temperature, the hot viscosity rating essentially establishes oil pressure - so there’s no reason to go too high on this part of the rating.
An oil sold as 5W-60 is no thicker than straight 5 weight oil under below freezing conditions and it is no thinner than straight 60 weight oil at 212°F.
The way you make a 5W-60 oil is to start out with a 5 weight oil
and then adding substances called Viscosity Index Improvers (VIIs). Without VIIs, the oil would thin out too much at normal operating temperatures.
This presents two problems.
First, VIIs are not lubricants, so the more of them that you add, the less oil you have to lubricate engine parts.
Second, VIIs are long polymer chain molecules that are broken into smaller pieces by the transmission gears in a motorcycle. This makes the oil less viscous at high temperatures. Synthetic oils typically have very few VIIs, so these oils are far less subject to viscosity breakdown and a result, synthetics are far more stable in a motorcycle engine.
A frequent marketing claim made for motorcycle-specific oils is that they retain their viscosity longer than automotive oils when used in a motorcycle. That is, motorcycle-specific oils contain large amounts of expensive, shear-stable polymers that better resist the punishment put on the oil by the motorcycle's transmission, thus retaining their viscosity longer and better than automotive oils would under the same conditions.
Nevertheless, when tested by MCN, the best-performing oil of the group tested was Mobil 1 automotive oil. Based on their test results, here's their advice:
1. Use a synthetic oil. The viscosity of synthetic-based oils generally drops more slowly than that of petroleum-based oils in the same application. There is no evidence that motorcycle-specific synthetics out-perform their automotive counterparts in viscosity retention when used in a motorcycle.
2. Change your oil more frequently, and more often than 3,000 mile intervals that is normal for cars. Motorcycles are somewhat harder on an oil's viscosity retention properties than cars. (The gears in the transmission are the significant factor in cutting the VIIs molecules into shorter pieces that are less viscous.)
A 5W-60 oil will have a lot of Viscosity Index Improvers added to 5W oil, so will experience a larger loss of viscosity over time than say, a 15W-50. So if you use an oil with a lower winter weight rating you’ll need to change it more frequently
I use the Mobil 1 automobile-specific in the 15W-50 viscosity only. Thinner viscosity versions of Mobil 1 make them inappropriate for both wet and dry clutch applications in my opinion.
http://ducatisportingclub.com/xmb/vi...=6566#pid53390