I'm wanting to switch to Valvoline 10w30 semi-synthetic or 10w30 full sythetic - will 10w30 hurt my motor...or help it? Car is never parked outside during cold months, and it gets 100+ degrees here during the summer. Oil changes come every 3,000 miles (mostly highway miles) and I only use K&N oil filters or Mobil 1 oil filters.