Brand name is all marketing. If the oil meets the specifications in the manual all is well.
Ya, all brands are not created equal but who cares? I certainly don't.

Does anyone here realize that the 5w20 oil that you are putting in your engine is a synthetic blend anyways.

I have been using Mobil 1 0w20 for 20,000 miles.

It seems that there is a little misunderstanding concerning 5W20. While some of it is semisynthetic blend (group I and group III), there are other companies that have pure mineral oil (group II+) for the same grade. While I do not know which company is using what, I cannot recommend a specific brand.Rule of thumb is that the less expensive 5W20 is fully mineral, hence safer for the rotory engine. But the blend is OK too, and both should burn much easier than a full synthetic based on PAO (Mobil 1, etc.). Also, the burning does take place in the engine and in the converter and I doubt anybody would like to have either foulled.

PS "group x" refers to base stock clasification (I to V) and is defined mostly by viscosity index and secondary by the sulphur content. The higher the group, the higher the index and lower the sulphur. BTW, PAO is Group IV.

I have been using Quaker State 5W20 since day one. I chose that particular brand because it seems to rank right alongside the Pennzoil that I would have preferred but costs a bit less. Never a problem, and my oil pressure gauge has never wavered from the slightly right-of-center position(haha).

Charles

Total crap. Synthetic oil burns, and it burns just fine. Try it yourself - take a pan of mineral oil, and a pan of synthetic oil, and hold your butane torch to the oil to ignite each. There you go - burns just fine. If you let them burn off completely, you'll also debunk another stupid myth about synthetic - that it doesn't burn cleanly. Check for any residues left in each pan after they've burned off - you'll find that the synthetic pan is probably cleaner than the mineral oil pan.

Regards,
Gordon

Given high enough temperatures, all carbon-based material will burn, no need to use a torch. However, synthetics burn slower, that's all. It the drawback for rotory engines but desirable for usual applications. The reason is their chemical structure. I think the synthetics will burn in the convertor and that would tend to raise the temperature. This might be why Mazda is suspicious of them, after the seal issue was solved. Sure Mazda did not ban them, but it does not endorse them also. And from what I see for brands like Saab and BMW, dealers love to used synthetics when possible because their profit raises as well... So I doubt is to the advantage of Mazda dealers to not endorse synthetics.
Just my $0.02

How do you know Mazda is suspicious of synthetic oil? What makes you think they do not endorse them, because they are not mentioned in the manual?
The only oil that is endorsed is a 5w20 IPA SL service rated oil. There is no mention to use or not use synthetic, or to use or not use conventional oil.
Ya I have read this and that on the web. All the experts, and racers, and mechanics, and all of their cousin's, brother's, and "some guy that fixes rotaries", etc.
It doesnt matter what anyone in person, or the internet says.
The only thing you should take as gospel is the owners manual that came with the car.

Hm, seems like confusion still reigns.... The way I see it, it is about playing safe. The 5W20 SL set of perfoemance tests have absolutely nothing to do with the issue on hand: speed of burning when inside the combustion chamber (fact). In fact, their lower NOVAC means less volatility which usually correlates with slower burning too. Now, Mazda does not recommend the synthetics (fact). OEMs like Saab or GM (Corvette) ask specifically for it, i.e. Mobil 1 (fact). The real question is, did Mazda tested synthetics in this engine (rotory) or not? I did not see anyone claiming it did (fact). Do people use them? Yes (fact). Is it OK for everybody to use them? I doubt. Why? Because a blend 5W20 is already good enough even for sporty driving - and most owners of RX-8 do not track their cars anyway. So why risk it and use full synthetic? Because they are slightly superior for piston engines? To me, the probable issue might be with the catalyst, not the engine. Dirty ignition plugs can be cleaned/changed (gas milage might suffer though). A burned out cat can be changed too but it's more expensive... Myself, if I could know which motor oil company uses Group II+, I'll be totally happy with using that one only. Until then, I'll get the oil change at the Mazda dealer (as it seems the next safest thing to do). Just in case something happens under warranty to the engine/emissions... After the warranty expires, I'll probably switch to full synthetic and put a FI on my auto RX-8 as well :)

blah blah blah lee dah. PLay it safe? Follow the owners manual. Period. Mazda specifies what oil to use. If it was bad for the car it would say in the manual. Burn/not burn? Ash/no ash? did they test? dunno. who cares. 5w20 oil semi synthetic oil. Why would they specify an oil that is half bad for your car. Nonsense.
Lets kill this issue.

I spoke with the dealership and they said the synthetic is no good for rx-8.

At 1 quart per 1000 or 2000 miles, combustion of oil in the converter isn't going to make much of a difference in operating temperature. Like throwing a match into a furnace.

The gauge is not working (kinda).
It's always in that position or totally off. It's like on/off.

Well, if the dealership says it, then that's that, end of debate. There you have it, folks.

Bullshit

He was being sarcastic, Baller...

History.....
 

Mazda specifically told owners of early RX-7s NOT to use synthetic.

The problem was that (I believe it was an early formula of Mobil 1) synthetic would eat out the big 'O' rings that keep the coolant out of the rotor housings.

I was one of the first people on the planet to get a new engine due to the problem. I bought a fill of Mobil 1 in 1976 and put it in my RX-3. Within five months my 'O' rings were gone, and the engine drank two litres of coolant per day. Mazda put me in a new engine. :) (That was well before anyone suspected it was the oil.)

The 'O' rings in the Renesis are a different compound, completely immune to synthetics; use whatever oil you like.

S

Thanks, Gomez.

Heh heh, this debate fires some people up, it fired me up at one point (ask Nubo!)....when the red mist decends, you can't see the forest for the trees!

And on that point....StealthTL, the letter from Mazda I posted said the o-rings had "improved" longevity to synthetics....they still recommend a mineral oil in the Renesis. They didn't say the o-rings were "completely immune" to synthetics.
Although I use Mazda's mineral oil, I'd use a synthetic if push came to shove...

Gomez.

GomezGuy......
 

You are right, Gomez - 'immune' is probably too strong a word.

However, while the seals are now 'much improved', the technology of synthetics has progressed much faster - the old ones weren't even miscible with mineral oil!

Synthetics today still fight that stigma with wording like "can be safely used with all other modern oils".

S

Mazdaspeed:
When breaking in any engine (race or stock), use a low ash content, mineral-based racing oil (20W or 30W). After the break-in period, change to a mineral or synthetic racing oil (30W or 40W).
In Germany is Mazda Dexelia 5w30 full synthetic are recommend.
At the Starmazda Serie is synthetic obligation those are stock Renesis engines.
Mobil 1 0w40 has too much sulfur ash: ~1,4%
Mobil 1 5w40 ~1,2%

HD

Sounds like you are recommending it.

How can I recommend something I haven't decided to do?

What I AM saying is that based on everything I currently see and MNAO's deliberately coy stand (or non-stand) on synthetics I don't see any technical issues that would make it a bad idea.

What kind of oil do you run?
 

If you say 5W-20 non-syn, I'll smack you...

Seriously, I'm just wondering what brand everyone runs and if anyone thinks that one may actually be better than another. I've been using Castrol GTX, and it runs just fine for me.

Same here--Castrol GTX 5W-20. Can't think of any good reason to switch to something else.

full synthetic Royal Purple 5-20