Which oil to use
The most debated question in the community, bordering on a religious war, so I won't try to cover every point here.

It boils down to deciding for yourself.

Some go with 5w20, to stay with Mazda's recommendation in North America. Some go with 5w30 to go with Mazda's recommendation outside North America. Others go to 10w40 or even 20w50, the most common weights among RX-7s. The general arguement revolves around if 5w20 is too thin or not. Typically, you want to go with a heavier weight oil (higher numbers) the hotter the environment you live in. Many manuals outside of North America state something to this effect. So research up on it, and make your own decision.

Dino vs synthetic is another hot topic, with the main arguement revolving around if the strength of the synthetic is worth the cost, and if there is any better burning (or not better burning) than dino oils, and if any deposits are left behind that could increase engine wear. Mazda only recommends non-synthetic, but does not require it. Your decision.

One point to keep in mind is that OIL WEIGHT AND OIL TYPE HAVE NO KNOWN IMPACT ON ENGINE FAILURE METHODS. In theory, the only way that oil weight could impact an engine failure is if it is a bearing failure. Oil weight has zero impact on the internal seal lubrication. Bearing failures are incredibly rare. In theory, the only way that oil type could impact an engine failure, is if you subscribe to the belief that injected synthetic is worse to burn than injected dino. This is belief based only. No one has been able to provide evidence for burn quality one way or the other.


And yes, all weights of oils mix with all other weights of oils, roughly averaging the numbers. Half 5w20 and half 5w40 is roughly 5w30, for example. Not precisely, but close enough. Dino also mixes entirely fine with synthetic.