Engine oil Motorex or IDEMITSU

Idemitsu zepro eco medalist advanced moly 0w-20. Basically the same thing as Mazda's oil.

Motorex 60:1 piston and rings go 180 hours with out issue, could go longer but i change it every winter, powervalve has yet to need to be seriously cleaned in 3 pistons.

I went with the motorex recommended oil. Worked great.

You don't need to add any more additives to modern day oils. You said you will be using Mazda 0W-20 oil? This is one of the best 0W-20 oils on the market. It is made by Idemitsu for Mazda. It has very high Viscosity Index of 221. Most 0W-20 oils are around 170. This means it is one of the lightest 0W-20 at start up. This is what you want in the winter.