Will squirrels really not eat safflower seeds out of bird feeders?
Isn’t the best way to do this putting chili peppers in bird feeders?
Welcome. @Birdman1!
I’ve never known urban squirrels to be all that picky about seed. If they can get to it, they’ll eat it. About the only way I’ve found to keep them away is to get really creative with squirrel baffles.
Dusting the feeder mix with cayenne pepper works up to a point. Here in Denver, though, I’m convinced that the local population has developed a taste for super hot Tex-Mex. 
We don’t get squirrels here, but our rats LOOOOOOOVE chilli pepper 
I’ve found through trial and error that my backyard squirrels don’t seem to bother the “Cardinal Cake” very much. It contains: Oil Sunflower, Safflower, Millet, Cracked Corn, Gelatin, Honey, Dextrose. Any other seed cake that I put out and especially those supposed to attract woodpeckers and/or containing nuts (particularly peanuts) or meal worms, the squirrels will get into it and try to steal the whole cake in one piece if they can figure out how to open the holder. But that sunflower/safflower/millet/corn one apparently is not worth the effort to them.