I have many Harbor Freight O-ring kits - SAE, metric and nitrile (buna-N), HBNR, and Viton, plus an older large U.S. red-box kit. I've never found the HF O-rings to be defective rubber, but can't say how many times I've revisited an installed O-ring. More commonly, I find old OE nitrile O-rings in my older cars which have become hard and brittle.

I recall putting Viton O-rings from the HF kit on the oil filter shaft of at least one of my 300D. I think HBNR is superior to nitrile, and probably easier to source than Viton. Most consider HBNR only for AC, but if they survive that hot oil environment, they are fine many other places. Nitrile O-rings don't last as well in current AC oils like PAG and Ester.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans