I'd give Chemical Guys Orange Degreaser a shot. I had some denim staining on my white seats and tried everything else the internet and forums said to try, but this stuff was the only thing that worked. I followed these instructions:
I have a friend in the Bay Area who specializes in cleaning products. I've used a variety of them on really hard stuff both home and auto and they have been like magic. Toads Eye Enterprises, Scott Armacost, I will look for his phone # for you
Take your car to a reputable auto upholstery shop. These guys have dealt with stains, burns, and every kind of problem. They can either fix it or tell you that you have to replace., and even then some specialty shops, that do restoration, might even be able to duplicate the section of the seat. It's worth a try.
One thing you could test on an inconspicuous spot is pure kerosene. It's great at lifting oil-based stains. First make sure you have pure kerosene by placing a few drops on a pure white coffee filter. If it evaporates after a few hours totally invisibly and with no residual odor, then you have pure kerosene.
Since I planned on getting this info for when the seats do wear out I opened a support case with Tesla. Looks like the seat covers are around 440 or a little over 500 installed. Seat covers for the rears and front drivers are no problem.
For the front passengers seat you can change the back out but not the bottom due to an integrated passenger occupancy sensor. I guess it takes dark arts magic to tell if someone is in a seat. So if you mess up the passenger bottom seat cover you must buy an entire seat. It is not 100% clear if the drivers seat cover can be used on passengers side so I wouldn't risk it.
They quoted a little over $3,000 to replace all rear seat and front drivers covers. The entire passengers seat is $1,870.
I was thinking though perhaps if you have an early model 3 you may have to buy the whole rear seat. Do you have an early build?