A self-cleaning oven does great with the metal interior but over time leaves a baked on brown film which I assume is primarily grease.
I read a number of solutions including baking soda, ammonia and vinegar. None worked.
The solution turns out to be simple. Use a razor scraper to remove the hardened film. in the first picture you can see the clean left side and you will note the brown residue scraped off. The second picture shows the finished job.