just bought a 1996 yamaha virago 1100. has 11k miles. gonna change the oil and not sure what weight to use. summer is pretty much here in phoenix already been up to 110f. its got a vtwin. dont wanna spend a fortune on oil. thinking about rotella 5w40 synthetic ir mobil delvac 15w40 but was wondering if that oil was 2 thin for the az heat. should i use 20w50? just want some opinions on what would be best 2 use. thanks in advance