the ugly truth is that in a preventive maintenance schedule it's not just the oil change and filter change that matters , it includes a 30 point check of your vehicle to retain its worthiness. if the PMS of your auv has been facilitated outside the dealership most likely than not the dealership may likewise refuse to honor the warranty. but do check with your warranty booklet if there is such an inclusion in the provision regarding this particular issue.
The part about the warranty is definitly true. Its also true, that in theory a PMS contains of about 30 points. However many of these are just things to CHECK and only replace/adjust if needed. Like replace break discs, if they are worn, etc.
In reality very often a mechanic will skip many of the points, even the costumer is theoretically paying for them. And the PMS will then be little more than a change of oil + oil filter, pumping up the tires to the required pressure and filling up with wind schreen washing fluid. Things you might just as well have done yourself.
For me therefore its a completely legitimate decision to skip the PMS, once the car is outside of warrenty already, and just do the required change of oil, oilfilter, spark plugs, fuel filter and air filter outside of the dealership.
If anything else need to be changed, like brake pads or clutch, you will notice that soon enough, when the parts start to gradually fail (breaks becoming noisy, clutch beginning to slip etc.)
Also before purchasing a brand new vehicle, and in particular one with an extended 5 year warrenty, its not a bad idea to ask the dealer for a list of the expected costs of all the required PMS during the warrenty period.
Some car companies still require PMS every 5.000 km. And if the warrenty is valid for 100.000 or even 150.000 km, and you are going to actually drive that much, that is a lot of PMS visits to the casa! Which in all likelyhood won`t be exactly free.....
Better maybe then to get a vehicle with a more reasonable 10.000 or even 15.000 km PMS interval. A check-up and service once a year should really be enough for a modern car, if you use fully syntetic oil and dont drive more than 10-15 k km pr. year.