My owners manual say's I'm supposed to use 5w20 oil with my vulcan engine, and I have only used 5w20 Mobil 1 in it since I bought it. 5w20 seems rather thin for a pushrod engine, especially since I live in Texas where the long summers are over 100 degrees many days. My warranty is up :noes: , and I'm wondering if I can use Mobil 1 5w30 in the summer insted of 5w20. Did they change anything with the vulcan engine internally since I had my G2 taurus, besides a little more power and plastic intake that would dictate a thinner oil be used? Or is it just for fuel mileage reasons?