Thinking about swtiching to Amsoil synthetic from conventional 10w30. My car is a 95 jetta 2.0 with 105k miles with a few performance mods, so it gets driven fairly spirited. My questions are if i switch should i stick with 10w30? i live in RI, so winters get pretty cold, and summers are usually upper 80s, low 90s. also, im skeptical of Amsoils claimed 25k drain intervals. what is a good interval to change the oil at given the fact that i commute 60 miles daily from september to may? and lastly, what is a good filter to use and how often should i do a filter change? thank you for answering these questions