With a bandanna you can do many things.
You can check your oil with it.
You can wipe your hands with it.
You can blow your nose in it.
You can put it over your nose and mouth to disguise yourself or filter air.
You can wrap it up with a plastic bag, put some grease on it, roast it over the fire, and use it as a dirty susan.
You can use it as a sling.
You can shield your neck from the wind with it.
You can filter water with it.
You can use it as a rag.
Your bandanna washes easily and dries quickly.
Your bandanna is durable and may outlive you.
Your bandanna weighs nothing and is a simple imperative tool.
Do not be caught without it.