Warranty issues

I got a reply from one of my friends with regards to the engine flushing, the remark is as follow:

"I was just replying to your email and commenting on the feedback by the bloggers on your blogsite - particularly, some car manufacturers void warranties if third parties touch the engine during the period of warranty..."

Lots of NEW CAR OWNERS are worried about the issues of void warranties because of third parties servicing their cars. The fact is, besides the warranty concern, have any one car owners who knows about the cars, feel that the authorised service centers render a good service? Or ppl are just sending in their cars because the schedule or maintenance record says so...?
Yes, warranty is an issue for new car owners, but certain non-authorised service centre qualified mechanics sometimes do wonders and comes out with innovative an creative ways to restore and maintain the car's performance at a much lower cost. However, I cannot speak in general for everyone. I am only posting remarks by owners who wants more for their cars and at a value-for-RM cost...
Ultimately, the decision to send their cars to or not to authorised service centres depends on the needs, priorities and criterias of the car owners..