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!!
Any effect should be immediately obvious, shouldn’t it? If your clothes are still dirty after washing, that’s something you can see/smell/feel. Anything else that your average detergent claims to do is luxury.