We had a customer come in the other day with their 1999 ML320 for a routine "Service A".  While we were changing the oil, we saw the Tie Rod boots were torn and the Ball Joints also were very loose.  The car had 130000 miles and we don't normally see the Tie Rods this loose.  We told the owner about the problem, and they ask if they could wait until the next service.  We told him they were a serious safety issue and they cannot wait.  He OK'd the repair and we showed him the old parts when he picked his car up.  He was shocked at their condition and very glad we insisted that they be replaced.  Then he ask a  question we don't normally hear.  He wanted to know why we checked these parts in the first place.  He had only asked for a oil change.  He told us other shops change the oil in the past, and said no one had ever mentioned anything like this before.
We see the discount coupons and service menu's from other shops.  Normally they save this type of inspection for their bigger service.  The thing is, an experienced mechanic can do this sort of inspection with  just a glance.  It's as simple as opening your eye's.   A mechanic with decades of experience is able to "sense" when something is wrong.  This type of service is second nature to us and it never even occurred to us that we should charge extra for this.  Why would any experienced mechanic want to put someone else's family at risk?   Life can have some strange twist and turns.   You never know how mechanical failure might turn out.  It could be one of our family members that ends up involved in a accident caused by a Ball Joint failure on a customers car.  

But who decides when a part should be replaced?  When is a part truly bad enough to replace?  Some mechanics want to restore a customers car to the way it was when it was new.  You wouldn't believe how many mechanics have said, "if they can't afford the repair they shouldn't be driving a Mercedes."  This self serving attitude is one of the main reasons we'll see a new customer.  Owners get sick of feeling like they have to replace half the car every time it goes in for service.  A typical example is Brake Rotors.  Some shops want to replace the brake rotors every time the car needs brake pads.  Brake rotors only need to be replaced when they've worn below their minimum thickness or if they are warped.  Unnecessarily replacing parts takes money away from fixing things that really need to be repaired.  Customers will only spend so much on repairs and then they get rid of the car.  We know that people would keep their Mercedes longer if they had confidence in the repairs.  It's the reason owners question if the repair can wait.  Trust is a funny thing.  You can't see it coming.... but you sure can see it go.