It's true, using vinegar in your washing machine with every load of laundry has many benefits.
Mold and mildew grow in damp areas and using vinegar in every load of wash you do keeps that from building up in the washer. It also softens fabric and naturally whitens white clothing and keeps your dark clothes dark. And if you have stinky arm pits shirts it helps with that too!
Use one to two cups per load depending on the size of your load. And no need to worry, vinegar is safe for standard and high efficiency washing machines. It is also good for septic tanks and the environment. So the next time you are at the grocery store pick some up and give it a try.