I need some advice on what oil to use in my wifes 2000 Jetta. It has the 2 liter 8 valve 4 cylinder in it. I want to run it on 5K intervals. She commutes about 45 miles a day to and from work so it sees a lot of highway miles. The car is garage kept but does see plenty of cold starts as she parks outside at her workplace. The manual states a 5-30 can be used if 5-40 isn't available. Since I'm not using the 10k intervals, would a 5-30 be ok or do these engines like a heavier 10-30? I did a search of UOAs but the oils used were all over the board.