Antifreeze PEAK or OEM Mazda

The Peak coolant that is the correct color for your year, i.e. pink for the MkIV, is fine. I have been using it for several years with no problems.

I ran the euro Peak without issue for about a year but I was bleeding coolant and in desperate need of the cooling system overhaul.

My car is currently filled with the Peak Euro Blue stuff, works fine, identical to the OE BMW formula anyway

Last time I priced FL 22 at the Mazda dealer it was about the same as AutoZone I was surprised I thought it would be considerably more.

I personally use Peak brand coolant, and I've never had an issue for 100K+ miles.

Even though most will say to stick with G12/G13, I think that is where that "sand" comes from. I decided last year to completely drain the system - including engine block - and converted to Peak antifreeze. I have not had any problems since.