Go48

I don't get it. What's the fascination with synthetic engine oil? Why would someone spend 3-5 times the cost for oil when any benefits, if they truely exist, would be marginal at best? Is it that the change interval can be extended? Personally, I would want to change the oil at the same interval with either oil in order to get rid of all the undesirable stuff present in the oil after a few thousand miles.

If you can get say 200K miles on the engine using dino oil (and most would likely get rid of the car well before that anyway) the extra money spent on syn would be a waste. Where's the cost benefit?

I can see the benefit in using syn oil in the tranny and differential, since it's gonna be in there for a long time and, at least theoretically, will maintain it's lubricating qualities longer than conventional oil.

Gord96BRG

The benefits are real and significant, not marginal. It is up to the individual to decide if the cost is worth the benefit, but that there are benefits can not be disputed.

For example:
- much better flow at extreme cold temperatures. Most engine wear occurs in the 30 seconds following a cold start. When it's really cold, like below 0F, that startup wear is significantly increased, because regular dino oil becomes thick as molasses and takes a long time to pump through an engine to get to the surfaces requiring lubrication. Synthetics flow better at really cold temperatures, so get circulated to bearing and friction surfaces much more quickly and begin protecting and preventing wear much more quickly.

Extended drain intervals are also a real benefit, and oil analysis has often been used to prove that synthetic oils are still providing better protection at 10K miles plus. Do some reading at www.bobistheoilguy.com for more on the benefits of synthetics for extended change intervals.

(I use either the new Mobil1 5W20 or Castrol Syntec 5W20)

Regards,
Gordon

Nubo

Don't forget, changing the oil in the 8 with dual oil-coolers is nowhere near a complete oil change. Some of the oil you put in today is going to be in that engine a good long time.

bxb40

I've run before into this same discussion... My "distilled" thoughts after half year of ownership are the following: if one could buy in US the original Mazda 5W20 that was/is used in Japan by them to test the engine, everybody would be happy. Unfortunately, the US dealers use some variant of the Japan oil (which might or might not give the tested reliability - nobody knows) so all the US customers scramble to find the best oil available in US... could it be synthetic, a blend, or else... again, nobody knows. The only oil ever profesionally tested in the RX8 engine and approved is the Mazda factory fill from Japan. The rest are all speculations and somewhat of a roulette.... Even here some dealers might not even use the 5W20 but 5W30 (cheaper, of course). So no real warranties...

So maybe one of the RX8 online vendors we have here can import the Japanese 5W20 Mazda factory fill oil and help us here, in US

FYI: there is absolutely no dino oil qualifying for the 5W20 grade. All are either synthetics, or blends. Plus, the cold flow issue mentioned above, it is not true. All oils of the same grade pass the same tests, so either synthetic or just a blend, will have to flow the same at the test temperature. There is no such thing as better or worst - it is a yes or no test (a severe one, part of GF3 - will be kept for GF4 and it was missing in GF-1 and GF-2, when te above statement applied). More confusion? The test is run on fresh oils - neither synth or blends or dino went through a qualification test after 3000 miles in an engine, let alone the rotary one. Again, for used oils, other components from the oil degrade first and not protect the engine, so not a matter of base stock but of oil brand (as they do use somewhat different components in oils). What do I do? I use premix (do a search here if you are curious what that is) during cold months - maybe it helps cold starts, who knows? And 89 CO gasoline (ignites better). The oil I use is Valvoline Smokeless 2-Cycle High RPM one
High temperature or RPM protection is a different story and relates not to the base stock (synth or not) but to other oil components. The stability does depend on base stock - but engine oils nowdays can run and stay in grade for 10,000 miles. Who, ever, kept it for so long in an RX8? Nobody I've seen - so the "benefits" of stability of synthetics go down the drain anyway when changing at 3500 miles.
As for ways synthetics could potentially hurt the rotary engine, there are a lot of speculations - again, non is proven, so... it will be up to the Mazda dealer to void or not a warranty. You can always take him to court and ask him to prove your engine died because of using synthetics - he will not have any hard evidence of it - if they would, a HUGE label will be present not only in the manual, but also in the engine compartment. So yes, you are maybe safe with synthetics but don't assume your engine longevity benefits from you paying extra money.


No flames, please. Just my $0.02

hagar852

I have seen this on this forum many times. My mazda dealer said, and was very clear about this, NOT TO USE SYNTHETIC OIL. It is also on the oil cap on the engine.

Reading through this thread I noticed comments about temperature and viscosity, but nothing about the fact about the engine burning oil. This is the reason why not to use it.

Dino oil burns differently than Synthetic does and leaves nasty biproducts behind after combustion. Which over time will leave a build up of crap in the engine which I imagine will impede the engine's process of operation.

This is basically the reason I was given by the Mazda tech who is a certified Rotary Tech.

Shamblerock

My oil cap simply says GF-3 5W20

I was thinking the same thing about the burnt synthetic biproducts residue inside the engine and exhaust. That's why I am hesitant to use sythetic. Although the manual does not state specifically that you can't use sythetic oil, they claim no responsibility should you use anything other than what they recommend.

Tough call.

Vaillant

Are you sure about this?

Pennzoil lists a 5W-20 grade with their other dino oils:

http://www.pennzoil.com/products/mot...multi_vis.html

hagar852

The dealer must have given me an updated manual I guess. I have it in my Owner's manual, but don't know the page number and I don't feel like going outside to get it right now.

But definitely on the oil cap of the engine in my 8. It says Non-Syn 5w-20.

I will take a pic of it.

bxb40

I'll comment on their pdf data sheet data (base of that page).
Looks like they use pure Group 2+ (probably this is what they call "PureBase" base stock). Synthetics are either Group 3 or PAO (Group 4). The difference in quality between Group 2+ and 3 (which is considered synthetic in US, but not in EU) is not reflected much in performance. It is mainly viscosity index of the base stock, to a small extent, and that is corrected using a viscosity modifier anyway (and that plays a more major role in protecting your engines under operating conditions - but who knows what they use?!? cannot chose the "right" one, unfortunately - see my previous comment about performance retention of a used oil).
If it was a mixture Group 1 and 3, they would call it "semisynthetic" or "blend." Dino oils are the old Group 1 and cannot qualify for GF4 alone any more. The test data presented in the pdf on that page shows the excellent performance of the 5W20 oil (hence it meets the GF4 specs). A synthetic oil will meet the same criteria if it is 5W20, so the benefits are not that evident now days. The "normal" oils for GF4 are really, really performant...
In a rotary engine, I would use a Group 2+ versus a semi or full synthetic, as far as it is 5W20. It will for sure protect the engine and, when injected in the combustion chamber, will burn easier than a full synthetic (not proven, but definately will not burn worse).
I am not endorsing a particular brand as I don't know what viscosity modifier they use and for most, what base stock. That is important because they break down at different rates and the GF4 tests are not hard enough - plus the Renesis, having high RPMs, is ultra-rough on those modifiers. On top of that, we get in Renesis more fuel dilution than Otto engines, hence our viscosity drops could be even worse. The fuel economy that pushed Mazda US to 5W20 is not seen by people - maybe they use 0W20 when getting the mpg info So maybe the best bet is a thicker oil to start with... 5W40... with fuel dilution and breaking down in 1500 miles might become 5W30, and at oil change time, 5W20. Of course, nobody will do this experiment, so it is just a late night idea
For now I go with the dealer oils, assuming they use a 5W20 from Mazda US. In stores, I've thought about either Pennzoil or Castrol 5W20 GF4 (not blends or synthetics), maybe at some point I'll go with either.

Sorry guys for the technical and boring reply

robertdot

I'm merging several synthetic oil discussion threads into this one, and sticky it. We get this topic far too often.

scoop

bxb40 said:
Yes but the pour point is what you care about when it is -30 degrees outside and that is much different than the viscosity index. Pour points of synthetics are lower by several degrees as a minimum so Gordon is right, go look at "pour point" on some spec sheets if you don't believe . . . Regular oils get so thick you can hardly get them out of the container and into the engine. I don't drive my 8 in winter and I change the oil regularly so I have no problem following the recommendation and using dino oil in it. I don't see huge benefits in the risk/reward department in my particular case. My winter car has synthetic in it because it does make a real and noticeable difference starting in the cold. You can also hear the diference in terms of how fast the lifters pump up and quiet down after you start, just ask anybody with an older VW or Audi. It's basically standard operating procedure to switch to synthetic to quiet the lifters down . . .

Gord96BRG

Not true - any oil that meets API spec SL, 5W20 is approved in North America. Outside North America, Mazda specifies 5W30, so the Japan dealer oil doesn't meet Mazda's RX-8 requirements for North America!

Very true - forum member StealthTL has written this before.

Sure, it's true. Re the test you mention - what IS the temperature for determining the rated cold viscosity? IIRC, it's ~20C, but certainly nowhere near -20C. It is true that different oils that have the same viscosity rating at +20C can have significantly different viscosities at -20C. Check the pour points on different listings - dino oils of 5W20 will have a pour point of ~-35C, synth oils of 5W20 will have a pour point of ~-50C. Basically, a dino oil at -35 will be thick as cold molasses, while a synth oil at -35 will still flow - and thus be pumped much more easily.

Now, you can also test it yourself - get 1 litre of your favourite dino 5W20, and 1 litre of your favourite synth 5W20, and place them in your deep freeze for a few hours. Take them out, and see how each of them pours. There, you've just demonstrated one of the major benefits of synth oils for yourself! (Let us know how your test turns out)

Regards,
Gordon

Nubo

The manual also does not state specifically that you can't use non-synthetic oil. So I guess that's out, too.

jlg MRX-8

what level of consumption can be expected????

Go48

I think the most frequently mentioned number is about 1 qt per 3,000 miles (not km), but depending on a bunch of variables, yours could be more or less. If it is a LOT more or a LOT less, you should be concerned.

Also, keep in mind that the distance between the full and add marks on the dip stick is not linear, so add oil in steps checking the level frequently. After awhile, you'll get a feel for how much oil to add based on the level on the dip stick.

bxb40

1. Gordon, if this is true, then the only real engine tests run for the Renesis were using 5W30 oils - and those could have been dino oils for all we know....plus those have typical high shear high temperature (HS-HT, tested at 150 C) viscosities of 2.9-3.1 cP vs the _W20 with only 2.6-2.7cP. Not a good news.... Maybe I'll go with 10W30 from a good company then... no need for synth, though, all pass the same tests to qualify for one particular grade. The fuel economy on our cars is missing to start with, and in NJ one does not need 5W oils due to low temperatures, so why pay extra for it?

2. Not really, pour point is something obsolete, the real test is called MRV-TP1. And is part of the SAE J300 Spec for motor oils. Depending on the oil grade (not its constituents), ALL 5W__ will be run at -35C and should have a max vis of 60000 cP - but all companies aim for about 35000 cP. So yes, it will flow after keeping in the fridge (5C). That fridge test is more similar to Cold Cranking Simulator test (CCS), which for 5W__ oils is run at -30C (5W-20 has a typical vis of 5200 cP).

More good news: the new GF4 oils will have a used oil cold temperature testing as part of the IIIG sequence, so even more assurance.

I feel now people will start asking why would anybody used synthetics Of course there are advantages, but not in the areas discussed here by most people. Due to the base stock being a synthetic are:
a) Stability to oxidation gives less varnish and sludge deposits. But if you change your oil at 3500 miles.... benefit is lost.
b) Sulphur content also is lower (Group 3) or zero (Group 4, PAO) and that will probably save your cat in long run.
c) Needs less pour point depresant (so it flows the same but in time is more constant, does not thickens if it looses that component), Again, changing it at 3500 miles is a waste. Even dino oils that are GF4 will do the same even at 5000 miles (they are usually designed for 10000 miles drain intervals).

The myth is also true because the advantages of synthetics come mostly from the other components. Being a high priced product, it gets (usually, but not always) higher performance viscosity modifier and get better detergent-dispersant packages.

OK, too much info already... if I would not have a Renesis but a high performance turbo charged piston engine, I would only use Mobil One Synthetic. There are real reasons why it is used as factory fill for Corvette and turbo Saab, in between others... and no, I would not change it at 3500 miles. Stuff in the oil? Nothing bad, really, this is why there is a filter there. Some water and decomposed but still soluble oil components... if vis and other properties are still right (and the test do check all that), why bother wasting good oil? Sure it's not golden but brown - it does not mean at all that it is bad oil and it should still perform within the spec.

khoney

I must be misinterpreting this statement - a quick trip to my garage found both Havoline 5W-20 and Castrol GTX 5W-20 sitting next to my Royal Purple 5W-20 and Amsoil XL-7500 5W-20 in my cabinet. Both the Havoline and Castrol are pure dino.

bxb40

How do you know they are dino oils?
Do you use the term "dino" for anything that is not synthetic or at least a blend?
If this is the case, then Group II and II+ are dino oils even if (esp. the latter) have performance equivalent to a synthetic and better quality than a synthetic blend - which is poor quality Group I mixed with a little Group III.

khoney

I have yet to see a commercial automobile oil manufacturer that wouldn't advertise the fact (and charge extra) that the oil was synthetic or a synth blend. If you are aware of one, please post the name. And yes, I and just about everyone else on this forum refers to dino oil as a fossil-fuel based, natural, nonsynthetic product.

Umbra

So what are some decent 5w20 non-synthetic oils?

JM1FE

Castrol GTX 5w20

bxb40

Here is the confusion then: in US (but not in EU) both Group III and Group IV (PAO) base stocks are called "synthetic." However, the first is, by your definiton, dino oil, as it comes from fossil-fuel based sources - except it is highly and specially refined. Group IV, called PAO, are made by breaking and isomerizing the waxes separated when the Group I or II oils are made. This is the only class of real synthetics but - they do come originally from fossil fuels as well (as waxes).
So, if I got you confused, it is good Because that is what the "synthetics", "blends" and "semi" makers want to do - and the nomenclature of "dino" oils is actually completely misleading and helps them sell you "performance" you don't need (if you change oil at 3500 miles)...
Also, nobody is disputing that any manufacturer that even remotely puts in a "dino" oil some Group III can claim "synthetic blend" and charge you lots extras. That mixture is actually somewhat inferior to a pure Group II or II+ but guess what; these are not "synthetics."

As I said before, if you find oils 5W20 that are non-synthetic, you have one of these "cheap" Group II / II+ formulations. Good performers and probably better for our engines, for less money as well. The other options to make this grade are I mix with some III - and that would be blend/semi synth. To blend I with IV or II with III makes no economic sens though those would also be blends/semi. Full synthetics are III (in US) or IV (in US and EU), mostly in pure form.

islandsoon

Darned if the new video I just rec'd from Mazda on the RX8 doesn't specifically state "not to use synthetic oil as they aren't sure yet of the long term effects to the engine seals" I, of course use mobil 1. Now what...

SpacerX

Excellent points -- points I've raised in other threads. I tell people nowadays hat the term "synthetic" has become almost a pure marketing term. The marketers can claim just about anything as being at least a "synthetic blended" oil based on performance characteristics and the additive packages in the product. As far as I know, the only PAO synthetic oils out there are the "boutique" oils such as RP, Amsoil, Redline, etc, and then, you'd have to look at the data sheet to confirm it (that's my guess).

SpacerX

Most seem to think the Castrol GTX 5W20 is good. Some other 5W20 choices that I've researched and would recommend:
- Castrol
- Halvoline
- Chevron -- same as Havoline
- Conoco
- Motorcraft Synth-Blend (not really synth -- it's a blend of group II, II+, III stock) -- same as the Conoco
- Pennzoil

Bottom line I tell people to look for:
1. Use the recommended 5W20 rating
2. Look for the proper API service and ILSAC ratings
3. Use an oil that passes BOTH the Honda and the Ford Motor Company specifications for 5W20 oils -- the FOMoCo spec is the most rigorous, and it is specifically made for the new 5W20 oils

I personally use the Motorcraft -- $1.40 per quart and it's yielded outstanding performance, based on the used oil analysis data I've gotten from Blackstone