I have a 1999 Ranger XLT with the 3.0, 2WD, automatic transmision, 75,000 miles. (I do like the 3.0 by the way). I change oil and filter every 3-4 months, never over 3,000 miles between changes. I have been using Castrol GTX 10w30 conventional oil. I have been thinking about swithing to Ford synthetic-blend oil. What are your opinions on doing this. If I do switch to the synthetic-blend should I stay with the 10w30 or swith to 5w30 (5w30 is recommend in my owners manual). I live in Florida and 90+ temperatures are normal. The coldest it ever gets is the upper 20's, and that is very rare. What do ya think?