I have a 2006 Subaru Tribeca with a 3.0 flat six engine. I am looking for an oil recomendation. The manual states 3750 severe use and 7500 normal use intervals of a 5w30. We live in middle Georgia. My daily drive is a 4 mile shot down the hwy and then 35 mph casual drive (3miles) to work (7 miles total each way). When not doing my commute I try to avoid sitting in traffic waiting for traffic lights. Some hiway driving is done also. I drive moderatly. I prefer a synthetic oil and have used pennzoil ultra last oil change due to great deal on it. I have also used mobil 1 in the past on occasion. The SUV has 60k on it with out any problems. I do not tow with it. Any recomendations for my type of use? And would this driving be concidered normal use?