It's more about maintaining the engine and removing crankcase gasses so they do not mix with the oil and cause premature damage. The road draft tube is advertised to begin working its Venturi magic starting at 30mph. So all the time you are running your engine before that, crankcase gasses are just collecting.
Since our vintages were the last years to not have PCV as a normal feature, it is easy to replace the road draft tube with a PCV system. It's a relatively inexpensive upgrade that you can do yourself.
