I will chime in, I too was offered oil changes for my new 4Runner many many years ago. I took advantage of those and did personal oil changes in between service mileage.
He's not complaint against me my only complaint is I think the service technicians go to training school to specifically over tighten oil filters and drain bolts. That seems to be the standard with every dealership that I've ever had an oil change done.
So now with my new Toyota 24 RAV4 I'm giving free oil changes as well. But I am just doing them myself because it takes me literally 20 minutes to do an oil change on this car. They are the ultimate easiest oil change I've ever done.
But yes a well informed shopper and an educated shopper definitely has an advantage over a dealership or in anything for that matter.
That's just my two cents