The pink stuff was NOT made for auto radiators
The pink stuff (non-toxic potable propylene glycol) was developed specifically for use in marine and RV plumbing. There are two different automotive antifreeze products...the "old fashioned" HIGHLY toxic ethylene glycol and a newer different formulation of propylene glycol that has a much lower toxicity than ethylene glycol, but is not 100% non-toxic. Neither of these should ever be use in marine or RV plumbing systems...nor is the pink stuff (non-toxic potable marine/rv antifreeze) suitable for use in engines either. As for why not windshield washer fluid...in addition to a high alcohol content, it also contains solvents that are not destructive to the hard rubber hoses used in windshield washer, but can be destructive to the soft rubber parts in toilets and flexible PVC hoses. I'm a big believer in, if it works as well, won't do any damage, and costs a lot less, use it (for instance, why pay extra for "marine" TP when it's the same thing as "no name" TP for a fraction of the price?). If windshield washer fluid were a good substitute for the "pink stuff," I'd say go for it. But it's not.