The laundry detergent manufacturers are so kind to supply a measuring cap to use for their detergent, but unfortunately, it's too much. My laundry appliance technician told me that two tablespoons of liquid detergent or less is sufficient to clean a washload.
In many cases, it's a matter of adjusting down from this amount, till you are satisfied with your clean laundry. You can save a lot of money doing laundry over a year, if you cut down and find a more appropriate balance.
There's another reason besides saving money, to reduce the amount of detergent you use. It could be the catalyst that sets the stage for washer odor.