Ok, here's my best advice. Go to this site
http://www.blackstone-labs.com/
call them on the phone and ask for a oil test kit to be sent to you. It's free and will arrive in a few days. When you're getting your oil changed, I'd suggest as soon as the kit arrives, collect a sample as directed by Blackstone and send it to them asap. They'll evaluate the oil and tell you what's going on. Think of this like your doctor doing bloodwork on you. Before major problems crop up your oil will likely indicate a problem. Now this report won't help with the steering problem but it sounds like they're just throwing parts at that. Once your oil report is back that'll give you some direction.
Piper