After 2+ years of cleaning a big mexican chain I can give you a suggestion I know for sure will work. CTI (ProsChoice) Prozyme and their Energy to boost it. 5+ minutes of dwell (10-15 optimal). Apply very heavy, twice or even 3 times what you would do for a residence. Cleaning restaurant carpet is what I like to call a "chemistry" job more then it is a best tool and heat job. A good formula will make or break the job. I tried soooo many different detergents. Wished I had used CTI's stuff in the beginning. Good luck.
If you say the carpet is not that bad and Grease Eraser is not working then your doing something wrong! For SEVERAL years Grease Eraser has easily cut heavy grease at extremely nasty Chinese rest.. Make sure you let it dwell, aggitate and use high heat..
However, if you do not have one:
Any enzyme pre- spray from a respected manufacturer + a good 175 agitation + a good high flow rinse with any respected manufacturer alkaline rinse will be just fine.
Everybody swears by their favorite products.
If they are from a reputable manufacturer, they all work quite well.