Correction: The worlds greatest
Hack spotter.
Did you know you can save even more money by making a better "Fels" yourself? Yes, you can. Use "el cheapo" Zote laundry soap bar, instead of Fels, as your base. Then add 1% BBQ charcoal lighter fluid (stoddard solvent) to Marty's gel concoction. Ah, what the hell..... Use 2% lighter fluid if you want a nuclear version. Use the white version of Zote, if you can find it. It makes for a far more "professional" and manly spotter, than the pink variety.
You see, Fels removed the charcoal lighter fluid in their product in 1988. The Hacks are now getting screwed over with even a lesser substitute since 2009, that isn't much more than a diesel-like fragrance (Camphor).
p.s. You can even "boost" the Zote spotter even more, ...use a "tweaker" trick of adding a few crystals of Red Devil Lye (Sodium Hydroxide) for every 6 ounces.