I suggest you start using a synthetic oil such as:
1. Mobil 1 4x Racing oil
2. Amsol or
3. Rotella, which is a very good oil but definitely not a pure synthetic, no matter how large they print it on their container.
Also there are better Oil filters:
1. Mobil M1-110 - $12
2. Purolator Pure One Pl14610 - $6
3. Bosch 3323 - $6
bosch oil filters are junk and i use K&N oil filters which are better than any others i have family that are mechanics and have researched oil filters and the yamalube is full synthetic.