I have a 06 civic with the 1.8 sohc engine and 5 speed auto transmission. I am coming up on 5,000 miles and plan on dumping the original oil even though my oil life monitor says 50% remaining. I live in humid hot SW Florida and travel 70% of the time on the highway. I was inbetween using Ford Semi-synthetic 5w-20 or Castrol 5w-20 (both around $10 for 5 quart jug) which meets Ford's high specs too. Also tossing the idea of Walmart's Supertech full synthetic 5w30 or 10w30 since it is onlt $12.24 per 5 quart jug. Which do you recommend and why? BTW, I am using the Walmart SuperTech filter which claims to be very good.