Car oil, doesn't matter how good it is, is not to be used for motorcycles. Car engine oil has most the time added friction modifiers which make your clutch plates act like a ice-skate course...
The faster you get the oil out of your engine the less damage is done.
If you have used automotive engine oil with friction modifiers you first need to clean the engine with a cleaning liquid that dissolves oil. I used gasoline once, but you can maybe find something better
I got a great deal on synthetic car oil so I bought some packs for my motorcycle. Now the clutch is slipping and the transmission sounds louder for some reason. What's up?