What the best yamaha 4t motorcycle lubricant oil?

Oil is sometimes subjective. Here are a few things to watch out for when selecting oil. If you have a Japanese bike you probably have a wet clutch. If so, make sure you use an oil designed for motorcycles. Wet clutches have been known to slip when exposed to some of the friction modifiers added by the API (American Petroleum Institute). I hear good things about mobil 1 motorcycle oil. Castrol has a number of good motorcycle oils. I personally use Belray Synthetic in my 79 KZ1300 A1. Here is a technical FAQ for oil: <a href="http://www.ibmwr.org/otech/oilreport.html" rel="nofollow">http://www.ibmwr.org/otech/oilreport.htm…</a> Keep in mind the FAQ was written from a BMW owners perspective. BMW's have dry clutches so again if you own a Japanese bike you will want to keep this in mind. Good Luck! P.S. I think the difference between semi synthetic and non synthetic is semi synthetic is synthetic oil blended with mineral based oil. The synthetic oil enhances the properties of the mineral ...  more