I am using a liquid detergent and I use exactly the half of the detergent they say I should use. If a the washing machine requires 1 cup, I do half. Mostly because I don’t trust the company to put me over their interests.
Now, what will happen? Will my clothes end up staying dirty? Will it not remove stains which a full cup would have removed? Will surfexcel kidnap me and torture me for not obeying their commands? Help meeee!!
For washing clothes, remarkably little soap is needed to clean ordinary soiling. Washing machines are very efficient. Using too much, besides simply being a waste, can accelerate the degradation of some fabrics, shortening the life of your clothes, and on the extreme end it results in overproduction of suds. Most washing machines from the last 30ish years will detect this and stop their cycle until the suds have died down, so it also wastes time.