Experience

Owww! My laundry is too heavy, I'm never going to get it up to my apartment. Maybe I should just leave my detergent in my trunk from now on?!

It freezes, AND you'll have to wait for it to melt the next time you use it.

Ah, I see you've tried this?

Yes, AND liquid fabric softener is basically ruined once it's been frozen.

Good to know.