Our car has done almost 30K miles and I have never seen the service letter A appear. (Change oil) Every 7k or so I seen B. (change oil and filter etc.) Has anyone else experienced this problem?

Also, I use regular Castrol oil (5w-15 I think) and it' s almost $3 a quart compare to my usual 10-30 for the Civic whihc is about a $1. What's so special about this grade of oil?

Sujit