An easy way to get burnt oil out of your oven is to spray the burnt on oil with some Easy Off Oven cleaner.
You can buy online some fume free easy off oven cleaner that works just as good as the other easy off oven cleaner but without the fumes.
I always use the easy off oven cleaner to clean any burnt oil or stuck on food or grease from inside my oven.
Spray the burnt on oil with the easy off oven cleaner and then allow to sit for 10 minutes or so and then take a scrub brush and scrub the burnt on oil out.
You can also use vinegar and baking soda to clean the burnt on oil or some degreaser.
But the easy off oven cleaner is stronger than baking soda and vinegar and will work much better.