I have a '95 s-10 with 138000 miles on it and got the truck at 98,000 miles. I have been using castrol blend 5W30 with 3,000 mile oil changes. The driving is really soft about 70% of the time and hard as all **** the other 30%. I live in Northern Virginia which will get near 0F in the winter and above 100F in the summer. I am going to start using 10W30 when out of winter months. What oil should I be using, Castrol blend or some other brand/type. Thanks for all the help and advice.