I did a job yesterday for a customer just moving here from Israel to teach at MIT. He bought a large but stylistically very dated townhouse condo. If this were still the early to mid-80's, this place would be cutting edge: shiny aluminum wallpaper; floor to ceiling mirrors; black marble foyer; and room after room of dingy, deep pile, white carpeting, that was original to the construction date of 1985. I told him at the outset of activities that he shouldn't get his hopes up too high - that this carpet was well beyond its reasonably estimated life length. He said it would all be replaced eventually.
To do the job, i used Bioforce's OUTSOLV, and boosted it with sodium percarbonite - an oxygenated cleaner.
I sprayed somewhat more heavily than usual, then did a pre-scrub in each room with a green-striped pad. Finished up with all-cotton Argo 2-sided pads. He didn't say much during the job, but when it was all done, he looked out across the now substantially brightened living room carpet and said he was really impressed with the results. It's always gratifying when you can get impressive results with 24 year old white carpeting.