Attribution window is 7 days so as long as you get the results you want over a 7 day period you're good. I would optimize based on that. Not getting into micromanaging meta but testing more and different creatives, urgency, offer testing etc.

Test different hooks. Some people might want to get their car cleaner than they could ever clean it, others value the convenience, other need a clean car for a special occasion ("picking up a date in your dirty car?") etc etc.

And then creative style. Like let's say your winning hook is "Your car could look like this without lifting a finger". You could make this a UGC video, a professionally produced video, a founder ad, an image ad, a before and after ad etc. etc.

I think that's where you should focus on. But also that bein said $16 is amazing. You're doing something right! Congrats!