This is an amazing video. Not because it shows you how to get oil stains out of carpet, but because it is such a terrible way to spot clean carpet. As a carpet cleaner in Tampa FL I wont focus only on the use of Windex as a carpet cleaner but let's also look at the application as well. First let me say that grease and oil can be emulsified by a lot of different things, not all of them should be sprayed into your carpet. Windex is a very powerful cleaner that has a high pH and can take on a lot of tough spots. It also has ammonia in it along with some other toxins that can cause respiratory issues.
No lets discuss the application of the Windex. A spray bottle is a great way to apply cleaners to just about any surface. In the video they agitate the carpet fibers by scuffing it with the bottom of their tennis shoe. Granted the carpet is agitated but it's also getting scratched. In Tampa FL we have sand everywhere and it scratches your carpet by just walking on it. You can only imagine how much damage is being done by kicking it into the carpet. I would recommend a much gentler massaging of the carpet instead of kicking the life out of it.
In the video they do remove the oil from the carpet but I would not say this how to get oil stains out of carpet because it's just to rough on the carpet. You could use some Isopropyl alcohol and water mixed together and get he same results. They are the main two ingredients in Windex and they are much easier to extract than Windex.