I think I read somewhere that each 100# = 1mpg. So the extra occupants + cargo would yield -2 mpg. Also, the EPA estimate was likely achieved at lower highway speed and so I think considering everything, your 5mpg hit was reasonable
Honestly I wouldn't bother because the padding sucks on the armrest so a new one likely wouldn't help. Maybe the newer models will have improved padding? But I couldn't find the exact part number.
#8...
I think it's normal for the level to fluctuate. If you really are losing coolant, you'll smell it and you'll have a stream of green crust running down the block.
As other people mentioned already, The filter should spin on freely with zero resistance. If it doesn't, then something is wrong. If you force it and a thread breaks off then you'll have a bigger problem. I say leave it for now if the leak is not too bad
Not an expensive part but didn't looked into the ease of replacing it
Part #9
https://mazda.oempartsonline.com/v-2020-mazda-cx-9--signature--2-5l-l4-gas/engine--engine-parts
I'm embarrassed to say I slightly cross threaded that bolt myself when I did my spark plugs... Kinda good to know this bolt is cursed and it's not me lol
@Favre95 I can feel your frustration thru the screen. To be fair, corporate level failed you by not standing by their product and the dealership failed you with crappy work. I hope once the link to submit claims is verified, you can submit your case for a full reimbursement.