Oil is to engines and transmissions what blood is to humans. Hmmm. Kind of… Oil serves many purposes like lubrication, cooling, efficiency, anti-rust agent, protection etc. These are the 3 most common questions about motorcycle oil. Spectro Performance Oils explain:
1- Question: Can I mix viscosity grades? Answer: Yes, you can and no harm will be done. Topping up with 10w40, if its all you have available, will not injure the 20w50 in your crankcase. It will, however, lower the overall viscosity of your crankcase oil to a certain extent. This will cause no harm to your motorcycle. Likewise, adding a 20w50 product to 10w40 will slightly increase the overall viscosity in your crankcase. Again, no harm will occur.
2-Question: Should I use a straight weight or multi-viscosity product? Answer: Multi-viscosity products are the preferred product in modern engines. They offer better flow upon initial startup and are more heat stable than straight weights. In the vast majority of motorcycles and particularly 1970 models forward, multi-viscosity is the preferred product. Older and antique models may require straight weights of SAE 40, 50 or even 60 in some early Harley-Davidson models. Your owners manual should be a useful guide in viscosity selection.
3- Question: I had read that high levels of phosphorous and zinc in motorcycle oil is harmful to catalytic converters in motorcycles. On your website, it states that your motorcycle oils have high levels of these minerals for specific motorcycle needs. Would your oil have an adverse effect on motorcycles with catalytic converters? Answer: No, there will be no adverse affect on your catalyst. The motor oils for the first 20 years of catalyst use in America were designed with these levels of ZDDP without any problems. However, vehicles with unusual oil consumption problems and very poor maintenance history could encounter catalyst clogging around 100,000 miles. The laws were passed to restrict the levels of ZDDP in oils for the benefit of these vehicles which do NOT include motorcycles.