My "genuine dealer service" accidentally put power steering fluid into my brake system ruining it.
At first they were going to fix it but once it went north of $3000, they balked and said a prior maintenance 7,000 miles previously might have put the fluid in (since i came to them for the one 3,500 miles before).
In the end, they gave me a verifiably good deal on a replacement new car when I pointed out they could fix the car for almost "free" since it was mostly labor.
Since then, I always tell the service tech this happened on a prior visit before they start and I always check the fluids before I leave the lot.
But there is nothing magical about a particular mechanic.
I agree on the warranty. Now that I've retired I will probably be exiting 'new car land' in another 5 years and be in the land of used cars again.