Regular or Synthetic
 

I have read a number of different posts about people arguing about which oil is better, but are there any hard facts to prove which one is better???

READ THE MANUAL. Whatever it says, do it. STOP. :) Those are the best facts.

Well, the manual may just be going by what they endorse, but do they really go by what is best for the car's performance.

The manual specifies 5W20 oil that meets API SL specifications, that's all. It does NOT say anything about mineral or synthetic - so as long as your 5W20 synthetic meets API SL, it's great as far as Mazda is concerned.

As for which is better - there's absolutely no doubt that synthetics are better oils - what it really comes down to is whether the benefits are enough to justify the higher cost, and that always seems to be a personal value judgement. For the technical discussions (the "hard facts"), visit www.bobistheoilguy.com .

Regards,
Gordon

Some reasonable assumptions, might independently help verify what they recommend.

Possibly, a performance car would logically be designed with performance inducing components. The RX-8 indeed is that. Well, 5-20w is certainly a lightweight oil, purpose formulated for both low friction function, and higher engine efficiency reasons. So far, so good. Then, in the rotary's function of dispensing oil to the combustion process, metering a light oil makes sense for optimal dispersion in the combustion chamber.

Possibly, given the rotary's self-destructive history, using an oil that promotes longevity would be a goal to enable Mazda to keep selling them long term. So, seemingly, our low weight oil has that benefit, at least in the rotary, as well.

As standards for consumer oil need to be met or exceeded in order to state this on the can, whatever performance, lubrication, and logevity engineering goals Mazda had apparently are met by the minimum oil specs listed. IMHO anything beyond that may be beneficial, but I doubt there is further documented proof at this point in RX-8 history to that - other than urban legend - race cars not included, as the RX-8 is not normally meant to be one.

Beyond that 'what is the 'best oil' for the rotary is a fun, harmless sport, and everyone can have an opinion for discussion. :) So I vote for What Mazda endorses is best for the car's performance and longevity.

Is it true that synthetic does not burn off as easily as synthetic?

There are rumors that synthetic produces sludge. I am not a chemical engineer. I don't know if this rumor is a fact.

I am also under the impression that synthetics burn at higher temperatures. According to Valvoline's website: "Compared to conventional motor oil, SynPower full synthetic motor oil offers easier cold starting, quicker flow upon engine start-up, quicker heat dissipation and better high-temperature properties."

The Renesis, it seems, was designed very very specifically. My question is whether or not the engineers planned on the oil burning away "quickly" as a 5w20 would and tuned the oil pump accordingly or if they just put X amount in at a time and don't worry about it.

I had a talk with one of the shop guys at Trussville Mazda the other month. They said the '8 didn't need synth (and, further, didn't come with synth as my dealer at a different dealership had told me). They argued that there are certain rumors about synthetic oil, and there are none about mineral oil. They didn't know if they were true either. So, be safe and go with mineral.

I don't think that a synth oil would produce significantly better performance or engine life. So, when the time came, I went with mineral. It's cheaper and proven.

HUH?

Let's presume you meant "is it true that synthetic does not burn off as easily as mineral oil?" ;)

No, it's not true. In some of the actual tests of the physical properties of various oils, synthetics typically shows higher flash points - basically, that's the temperature at which the oil evaporates. Synthetics have higher flash points than mineral oil, given equivalent grades - but that's a good thing, because I'd rather not have my oil evaporating when my engine is hot.

The flash points, however, are much lower than combustion chamber temperatures, and synthetic oils BURN just fine. In fact, synthetics burn much cleaner than mineral oils - I have no idea where the rumour started that synthetics leave sludge, because not only do synthetics not leave sludge when burned, it's mineral oils that leave sludge!! (from the wax in the crude oil that isn't removed in the refining process)

Regards,
Gordon

Most of the rumors about sludge, not burning cleanly or properly, etc are just that...rumors. And of course there are plenty of rumors about minteral oils as well, especially about <insert favorite brand to bash here>.

I'm not a chemical engineer either, but from what I remember reading the high temperature properties of synthetics do not mean it burns at a higher temperature or a different rate. Plenty of people on this forum do know more about the technical details, so if they're not tired of chiming in every few weeks when this conversation erupts, maybe one of them will do so.

One thing I do know....synthetics (at least Royal Purple, the one I've used in the past) retain their lubricating properties much longer in the presence of fuel dilution. I haven't seen anything to indicate one way or the other as to the performance of the Renesis in this matter, but the 13B-REW was notorious for this.

jds

No, it's just a nasty rumour. Synthetics leave less residue than mineral oils.

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I am also under the impression that synthetics burn at higher temperatures. According to Valvoline's website: "Compared to conventional motor oil, SynPower full synthetic motor oil offers easier cold starting, quicker flow upon engine start-up, quicker heat dissipation and better high-temperature properties."

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No, synthetics burn just fine - it's their flash point that is higher (evaporation), which is one of the better high-temperature properties.

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The Renesis, it seems, was designed very very specifically. My question is whether or not the engineers planned on the oil burning away "quickly" as a 5w20 would and tuned the oil pump accordingly or if they just put X amount in at a time and don't worry about it.

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Oil science isn't magic or that precise. Note that outside North America, the identical Renesis engines have factory specified 5W30 oil instead of our 5W20. We get 5W20 to get a teeensy improvement in EPA mileage ratings, that's the only reason. Also note that European Mazda dealers are using synthetic 5W30 for dealer oil changes.

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I had a talk with one of the shop guys at Trussville Mazda the other month. They said the '8 didn't need synth (and, further, didn't come with synth as my dealer at a different dealership had told me). They argued that there are certain rumors about synthetic oil, and there are none about mineral oil. They didn't know if they were true either. So, be safe and go with mineral.

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No engine needs synthetic (well, very few anyway - Ferrari Enzos excluded!), but that doesn't mean they can't benefit from it's use. There's lots of facts about mineral oil, like wax content leading to sludge buildup, thickening at very cold temperatures which leads to poor protection at cold starts, poor viscosity characteristics at high temperatures, etc.

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I don't think that a synth oil would produce significantly better performance or engine life. So, when the time came, I went with mineral. It's cheaper and proven.

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It's fact that synthetics are proven to be better oils. They will make a difference in engine life - how significant that difference is, and how important that difference is versus the extra cost of synthetic oils, is up to the individual owner to consider and justify. Yeah, mineral is cheaper, and works well. Synthetics are proven better. :D

Regards,
Gordon

Gord96BRG... you're the man!

Amazing info! Thanks :D

I am still amazed at how many threads there are about synthetic oil on this forum. In addition to Gord....'s good information I would like to add:

Mazda have not tested the engine using synthetic oil, and do not recommend using it because of this. However, they are not saying it is worse than mineral oil, nor are they saying you are prohibited from trying it yourself.

One of the most important factors is heat transfer.

The apex seals on a rotary engine reach speeds much higher than the piston rings on a piston engine. I don't have the data on hand, but from memory it was 3 times faster.

The sealing of the apex seals is critical. Moreso than the rings in a piston engine. As temperature rises heat must be taken away from this seal and the rotor housing, partially by engine oil.

Synthetic oil has different heat transfer characteristics to mineral oil. This, combined with the fact that the oil is injected into the combustion chamber and burned with the air/fuel mixture, means that changing the oil type requires a little bit of experimentation by the manufacturer before just flying in and saying "go ahead"!

These may not be the only reasons Mazda do not recommend S oil, but they are important ones.

Mazda are testing synthetic oils on the Renesis as we speak, so it will only be a matter of time...

Cheers.

My bad, i meant to put MINERAL not SYTHETIC

i thought you meant to write that in a sort of sarcastic fit. i was going to follow on with:


but i heard that, for rotaries, synthetics aren't as good as synthetics?! and what about mineral oil vs. dino oil? or is it DYNO oil?

LOL, that would have been funny

Is Mobil 1 5W-20 an okay oil to use. I have heard that pennzoil synthtic is peraphin based, which leaves a sludge in the bottom of the oil sump. is this true???

Some Japanese aftermarket rotary tuners like R magic (SL 0w30), knight sports (SJ 10w50), and RE amemiya(SL,10w40) sell their performance oil, all of them are synthetic oil. These tuners are very famous in the field of totary engine tuner in Japan. Is there anyone having comment on it?

Where can you get these types of oils???

I think that i am going to go with Royal Purple

I don't know where to get them in the States, sorry.
In Taiwan some rotary engine tuners carry these oil in their shops

This has been an age old discussion with rotaries.

One thing is for sure, there have been no rotary engine failured from synthetic oil. Failures happen for other reasons.

on the Mobil 1 web site, under "Why Synthetics" then "Myths About Synthetics"

they say.

"Using Mobil 1 will void my new-car warranty?


With the exception of the Mazda rotary engine (Mazda does not recommend any synthetic motor oils), Mobil 1 with SuperSyn™ will not void new-car warranties. Mobil 1 with SuperSyn™ exceeds the API and ILSAC motor oil service requirements of all new-car manufacturers, both import and domestic. If in doubt, always check your vehicle owner's manual or contact your vehicle's manufacturer. "

Don't if this helps at all, ... i was ready to go buy some till i saw this...

???

I now await the wrath of the Dino naysayers....