Kia would not honor warranty

My car was brought in to South Shore KIA due to the engine burning oil. KIA has a 100,000 powertrain warranty. At the time my car had 88,698 miles and I was told I would get an oil change from South Shore KIA and return after driving 1,000 miles they would then determine if the car was really burning oil. It was determined I was burning oil and they submitted a request to the tech line which would approve the warranty covering a replacement engine. KIA needed my receipts for oil changes to prove I was maintaining the vehicle. I told them I had some but I may need to talk to my mechanic if he had copies. I was instructed by service that we would submit whatever we had because he needed the loaner car back. The tech line wanted to do a partial tear down which I was told I would have to pay about $400 if the claim was not approved. KIA tech line was provided a video of the tear down that was done by South Shore KIA. The technician doing the video can be heard saying the engine is clean no signs of sludge. The video shows a clean engine and I was told the purpose of the video was to prove it was being maintained since I didn't have all my oil change receipts. KIA tech declined the claim due to sludge. KIA is not honoring their warranty. Their own technicians have stated that the engine is clean and maintained. Many professionals including their own employees have maintained that the engine is clean of sludge and well maintained. I also have the video however I am unable to upload it due to the size