You're defeating the purpose if you mix the oil. The whole purpose of synthetic oil is the viscosity is much lighter than regular blend so it does not cause drag on the crankshaft, robbing you of horsepower. Believe it or not, you can tell the difference with synthetic oil! /images/icons/smile.gif
I would hold onto it until you buy more synthetic oil for your bike. It doesn't hurt to mix but synthetic cost more money.../images/icons/cool.gif
Yes it is okay to do this IF you have to. I do not usually mix oils, only on occasion if I'm low and there is no similar brand around. It will not hurt your vehicle. Synthetics do NOT have lighter viscosity than regular oils. If they did have lighter viscosity then they would have a DIFFERENT viscosity than the regular oils all together. Viscosity is a measure of the oil's ability to flow. If a synthetic is 5W40 and a regular is 5W40 then they have the same viscosity, period.
However, the difference between a regular and a synthetic comes into the synthetic's ability to change vicosity quicker with heat build up AND its lubricity. This where the synthetic has its benefits, not in its viscosity. This is where you also get your HP benefits.
Yes, most if not all synthetic oils will mix fine with conventional oils. Just keep in mind that the protection provided with synthetic is lessened. I would rather buy synthetic oil of differrent viscocity(?) than mix synthetic and conventional. Say 2 quarts of 10W/40 & 1 quart of 10W30 both synthetic would be better than mixing with conventional oil, imo.