Hi all, my girlfriend just aquired a 2010 Dodge Journey AWD with a 3.5 litre engine. The cap and manual call for 10-30. My cousin who works for Chrysler got us the deal on the car which had 1100 miles when we got it. He said that engine is tough on oil and I should run 10-30 summer and 5-30 winter. My question, why can't I run 5-30 all year round. Looking forward to hearing some thoughts by the pros.