First off, I've searched for the answer to my question, but could not find what I was looking for. I've decided to use 5w20 dino till it warms up, but what I haven't decided, is what brand of 5w20. I've read through many threads trying to find which brand is ideal, but I've had no luck. Does anyone have any insight on the best 5w20 (and 5w30 for the warmer seasons) to use in these cars? Also, please don't turn this into a weight or synthetic vs dino discussion, as I've 100% made up my mind on that already.

 

It doesn't really matter, whichever brand you want.

If you are interested in test data, take a look through the oil analysis thread.
https://www.rx8club.com/series-i-tec...m-here-184241/
or the oil test from Russia to see how oils break down from heat over time (the test ignores the results of stress and sheering)

If you aren't interested in test data, then the choice matters even less.

 

Data is exactly what I was looking for, thank you so much!

 

Consumer Reports tested that on some oils a while back. They found that Castrol stood up to shearing very well. Interesting, since at the time Castrol's advertising stressed that it stood up to viscosity breakdown. An actual truth in advertising!

Of course, CR did not test much (if anything) else, so you can't base a decision on just that. And now that they dropped sponsorship of John Force there isn't much reason to use the stuff.

Ken

 

I always use Castrol 5w-30 and so far so good...

 

Castrol Edge 0W-40 Synthetic FTW

 

Castrol 0w40 will only give more ash. Too much magneseum which produces harder ash versus other 0w40s. Stick with low magnesium oils FTW.

 

I ran quaker 5w20 in my last engine, 0w40 Mobile from now on.

 

Seems like M1 0w40 is a very solid choice. I'll have to see what my dealer says about it.

 

Your dealer will moronically say no, then falsely tell you what Mazda recommends even though in reality Mazda has always claimed synthetic for rotories and use dino for US only for emissions reasons.

 

Yeah, save the trouble and don't bother asking them. You stand a pretty good chance of having them tell you something that is patently false, based on a misunderstand of the rotary. Just because they work for a company that sells the car doesn't mean that they actually know anything about it.

 

Mod edit:
This is the new member forum, and flaming of newbies for what they ask is not permitted here.
-RIWWP

 

Just stating my opinion, if someone can't search the answers for simple questions like these then most people will start threads expecting to be spoon fed instead of searching.

Especially considering the various oil threads there already are. But I'll make a contribution as well, I don't want to come off that I just wanted to flame!

The brand of oil you use doesn't necessarily matter, as having clean fresh oil and topping off is more important. If you look at oil analyses and that Russian oil test. You'll come to the conclusion that synthetic oils are far superior to conventional oils.

I too use Mobil 1 0w40, whether for hot or cold climates it's a good option.

 

Any major brand - Valvoline, Castrol, Quaker State, etc. - is fine. And yes, far more important is that you change it regularly, and check the level frequently.

 

When you get a oil change at Mazda they put in Semisynthetic.

 

Rotella T6 ftw. I've been wanting to try M1 0w40 for a while now though. Might try some my next oil change.

 

Rotella T6 is also coming with higher magnesium now. Not good for us oil burners

 

Even better reason for me to make the switch to M1 0w40. Magnesium has a higher flashpoint I'm guessing?

 

It just leaves a harder, more tenacious ash when burnt exacerbating carbon build up issues. M1 0w40 has low magneseum so good choice in that and other regards. The other M1 flavors seem to have a good dose of magnesium as do the Castrol synthetics and many diesel oils for TBN retention so I'm personally weary of them in an oil burner.