Urup away..
Sorry, CleanFresh, have no idea what true "Naptha" smelled like so can only assume Fels smells like it as they advertise on the label "The Golden Bar with the Clean Naptha Odor".
The ingredient list on my vintage bars of Fels does not show any sort of fragrance, IIRC so guess it is the naptha talking.
Yes, Napthalene (aka "naptha") can be pretty nasty stuff, not something to be played with and was removed from the consumer market for health reasons. Speaking of kerosene, P&G who made a white laundry soap with naptha was sued by the feds because some of their product contained kerosene instead of the naptha per label. While all petrol base products/solvents will remove greast/oils, naptha is better than kerosene.
One must remember at the hey day of naptha laundry soaps, this was as good as one got for serious soil removal and over coming the limitations of using soap for general laundry. Modern detergents contain a cocktail of enzymes and other chemicals which have largely replaced petrol and it's by products on laundry day.
Being as the above may, NOTHING rids laundry of serious stains the way vintage Fels soap does. From greasy ring around the collar/cuff stains, lipstick, make-up, ground in dirt, some types of ink, and so on, just a quick rub with a bar of Fels has never let me down.
Launderess