RX8Club.com - Engine oil choice

Closed.

Oil threads get emotional and turn into war zones around here.

From my new owner's thread: New and Potential Owners START HERE! - RX8Club.com

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 SIGNIFICANT 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 real 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.

Quote:

There are 2 different "types" of oils (dino and syn)
There are 5 commonly available cold weights of oil (0, 5, 10, 15, and 20)
There are 4 commonly available hot weights of oil (20, 30, 40, 50)
There are 4 commonly available "Straight" weights of oil (20, 30, 40, 50)

So that means that there are (2 * 5 * 4) + (2 * 4) 48 different oil types/grades to choose from before you even get to BRAND of oil. I can think of 10 (Castrol, Valvoline, Mobile 1, Pennzoil, Royal Purple, Peak, Quaker State, Shell, Motorcraft, Mobile Super), bringing the number of options to 480.

Then we get into climate and driving conditions.

So even if you find that 1 person in 480 that you agree with 'in general', the climate conditions between you two are probably quite different, making an actual agreement unlikely.

And you know what the kicker is at the bottom of this whole oil debate pile?

It doesn't really matter

Fresh oil on regular changes is far far far more important than ANY of the above attributes. And the only impact that crankcase oil lubrication has on your engine's lifespan is bearing wear, which is not a severe concern for us, since we have numerous other methods of engine failure that have nothing to do with oil attributes!

Outside of lubricating the e-shaft bearings and being available for injection into the combustion chamber (where none of the attributes above matter at all), the oil's benefit is a secondary method of assisting to keep our engines cool. Oil is fantastic for transporting heat out of the engine. And all types and viscosity do that equally well, or as close to equally as won't make a tangible difference.

So if oil weight matters to you, then do some reading on the various opinions, find an opinion you somewhat agree with that is made in reference to the climate you drive in, the drive style you do, and your budget, and go with that.