Engine oil IDEMITSU or Pentosin

In terms of oiling, get a sohn adapter so your apex seals aren't being lubricated with crankcase oil, and instead are injected with rotary-specific oil, like idemitsu.

Subaru OEM oil is Idemitsu 0W-20. I currently use Idemitsu Zepro\* 0W-20, a high-moly formulation from the same manufacturer.

That's the wrong oil. You want the Idemitsu eco gold medalist advanced moly 0w-20, which is basically the same as Mazda oil(Idemitsu makes the mazda oil).

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

I bought a 5 Liter Bottle of Pentosin SAE 5W-40 Pento High Performance II Motor Oil from O’Reilly Auto Parts for $50.75. This API SN/CF and ACEA C3 Rated Oil complies with VW-Specification 502 00/505 00/505 01 and is Made in Germany.

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.

I like pentosin and motul

Pentosin is pretty cheap and good quality, thats what Ive been using the past couple years.

I have a 08 2.5 Been using Pentosin 5w-40 so far so good

5w40 pentosin vw 502.00+ oil. Hasn't let me down in any of my motors yet!