I have had my xr650r for 4 months and I had changed the oil when i got it. I used Amsoil full synthetic 10w40. That was 600 miles ago. Now I need to change the oil again before a major trail riding outing in Nebraska Halsey national forest. My problem is i can not get any more amsoil that quick. Would it hurt my engine any to change it with a different good quality oil? Or is it essential to run the same brand forever? As you can see I love my pig and want whats best for her.