I just want a simple answer here since I really can't think of one. I don't want this to turn into a synthetic vs. non-synthetic debate, I just want one good reason TO use synthetic oil in a rotary. Nothing more, nothing less.

I will never do it, but I'm curious what possible reason there would be TO use it, because I keep seeing people swearing by it.

 

https://www.rx8club.com/showpost.php...13&postcount=1

 

synthetics retain their lube properties longer and are more tolerant of heat due to their more consistant molecular structure and additives.

 

You don't need synthetic, just change your oil every 2500-3000 miles and you're fine. Besides at the cost of conventional 5w20 you could change it 3X for every time you change synthetic. Besides I'd rather have clean oil in my car than oil that takes more mileage to break down.

 

Oh, I know I don't need it. I've just been wondering why people like the idea of going against Mazda's clear instructions and paying 3x as much for their oil. I figured there had to be some reason other than HATE THE MAN. People with enough money to buy an RX-8 aren't usually THAT stupid.

 

with Royal purple, I can go 7000mi easily between changes, so it costs me only a little more $$$ than if I changed it every 3000mi. That and the better protection.

 

Point taken. I'm tracking my car, though, so I'm going to want to change oil after almost every track day, so I might as well keep using normal stuff. ;-)

 

In my case I asked myself the opposite question -- Why *wouldn't* I use synthetic oil, since synthetic is superior in most respects? I have see many arguments against synthetic in the last couple of years stating ways in which synthetic was "bad". None of them stood up to rational examination in my view, and I'd seen no real-world evidence to support them. The other class of arguments center around Mazda "saying" that synthetic oil was bad for the RX-8. However, "Mazda" in these cases was always an individual salesman, service writer, etc. Or in one case, an internal memo in Mazda Australia parts department. My 2004 Owners Manual said nothing about synthetic oil, and I took that silence to be Mazda's official stance. My oil met or exceeded API service classification "SL" as required. If Mazda wanted me to know they considered synthetic oil to be harmful, or even for it to void the warranty they would have to get off their butts and revise the owners manual or at the least provide a definitive statement directly to each and every RX-8 owner. Which leads us to....

Fast-forward Aug 2006, and now it appears that Mazda may well be ready to make a definitive statement about synthetic oil in the RX-8. Based upon that, and since I needed to change the oil, I have switched from Mobil1 to a mineral-based oil.

Not that this necessarily means that synthetic actually is bad for the car, but if that's Mazda's position I'm happy to comply and I'll just be glad if they settle the argument by taking an official stand on the subject. Now, if they would offer an explanation of the actual mechanism that causes synthetic to be bad in their view, I'd be even happier. The Australian TSB indicates the problem may have to do with carbon deposits at the edge of the intake port that are presumably more tenacious than the carbon formed by conventional oils (all oils form carbon). Seeing as how this is a low-temperature, low-pressure area of the engine, it's an argument I can't immediately dismiss out of hand.

What this means long-term is difficult to know at this point. Especially since the distinction between synthetic and "conventional" oils becomes less as time goes on. But again, if Mazda says so, in a direct and unmistakeable way, then fine.

 

Oh Oh Oh...I can answer this...becuase it COSTS more

 

My '05 came with a DVD from Mazda that says "use a non-synthetic 5W-20 Oil with SL or ILSAC Approval on the container label." That's "definitive" enough for me.

 

The problem with that statement is that once the oil says SL and the proper viscosity, Mazda has no grounds to specify anything more. There's a hefty infrastructure between manufacturers, oil companies and standards organizations that ensures that *all* you have to do to have the right oil is check the API marking.

I expect this is why they won't void warrantees if the problem really is due to synthetic oils. Their statement is good enough for me, but legally they can't freelance when it comes to standards like this.

Ken

 

I'm sure mazda also says not to use aftermarket: swaybars, tires, wheels, intakes, exhausts, catalytic converters, pullies, flywheels, brakelines, brakepads, rotors, or forced induction.

But after all is said and done, who has the better, faster car? The person that listened to mazda?

 

They do. And they'd love for you to have to get all service done by a Mazda dealer, etc. At one time they could do that, but laws were put in place preventing that kind of monopoly. All they can legally do is publish specifications and require that you use products that meet those specs. When it comes to oil, the specs are the API ratings.

I don't see how the recommendation against synthetic oil makes any more money for Mazda, so I'll believe them when they say not to use it. YMMV.

Ken

 

Why would you use any oil at all? How about water? They are both wet and both remove heat well. It's cheaper. Just change it more often. Use an additive.

 

Not everyone got a DVD. I know I didn't.

Where is the one place a consumer would look to see the oil requirements, or any specifications that the owner is expected to adhere to? -- the owner's manual. It's so obvious it hardly bears mentioning.

Just like you wouldn't look for the DVD if you wanted to know how many quarts the cooling system holds, or what type of coolant to use. It mystifies me why this one particular specification was treated differently and poked its head up in odd little places. DVDs, little glossy "tips" booklets, but not the one place that defines the maintenance requirements for all aspects of the vehicle. The "definitive" document, as far as I am concerned. This is why there are thousands of posts on this topic.

 

Hmmm. Maybe that explains why they've been so circumspect on this issue.

Can they get away with saying "not recommended"?

 

There is obviously at least 1 synthetic on the market that is causing issues. I don't see this as a problem with the fact that it is a synthetic but rather with the manufacturer and their choice of formulation. Why would I want to use any oil from this company? This company's conventional oil probably doesn't have everything in it that they put in their synthetic which just happens to be what is really causing all of the issues. This has led to a false notion that synthetics are bad rather than pointing at the real issue. Why hasn't Mazda said which company or companies make an oil they don't like? It's simple. They don't need a lawsuit against them from whoever they name claiming they make a bad product.

Remember when I posted at Sevenstock last year how I asked Mr. Rotary Engine himself, Yamamoto-san which synthtic oils he doesn't like? Remember also how it was a broekn english conversation so multiple names didn't come out. A few did though. Idemitsu (a group IV synthetic) is a good synthetic oil to use in a rotary. Of course Yamamoto-san himself helped formulate it so that's a good reason for an endorsement. The fact that he endorses ANY Group IV synthetics at all proves in itself that it's not a "synthetic" issue but rather something else. Remember it's the base stock that determines the group and it's the base stock that makes it conventional or synthetic.

Back to the topic at hand. He also said Royal Purple is fine. Valvoline is also fine. It is a hydrocracked Group III so whether or not it is a synthetic is a subject of much debate. Some say yes and others no. The only other name I got out of him when it came to synthetics was Mobil 1. He said not to use it in a rotary. He didn't say why other than to say it had to do with the oil metering system. I didn't get any more details than that. He did admit that while Mazda has tested and continues to test different manufacturers products, from apex seals to oils, they hadn't tested nearly all of the oils out there and need to play it safe by just not recommending any of them. That's a legal department talking.

What does this mean about Mobil 1 synthetic? Is Mobil 1 a bad oil? Nope. Millions of cars use it and have with no issues. It is actually the most widely used synthetic in the world which may actually explain things. If there is something that Mobil 1 used in their synthetic oil formulation (as we all know it's not the base stock that causes any issues) that happens to leave deposits in a rotary in greater quantity than most other oils do, wouldn't it just be safe to tell people not to use any synthetics? Remember Mobil 1 is the most widely used synthetic in the world. That alone means that most people that will us synthetic will probably think about using Mobil 1. It's a formulation issue not a synthetic issue.

Does this mean that MAzda has specifically stated that Mobil 1 synthtic is dangerous? Nope. They never will say that. This is just a result of a conversation I had with the bigdog rotary guy at Mazda and none of this can be considered an official stance. When you look at the puzzle pieces, you can pretty much figure out what is going on.

Why do I use synthetics? It's pretty simple. I like knowing that the oil I use is not the weakest link in the system. I like the added stress I can put on the engine and still not have to worry about the oil breaking down. I like knowing that my base stock oil that gets injected into the engine won't evaporate before it all burns off leaving the additives behind as unburned deposits. I like knowing that my synthetic has a higher flash point than it's evaporation point which helps to prevent this. Of course this also has to do with formulation but I know the synthetic that I use is good. I also only truly endorse 1 oil. Actually 2. I endorse 1 conventional and 1 synthetic and will only use those 2. The extra cost is minimal for this piece of mind and really only adds up to less than half a tank of gas in terms of money over several thousand miles. A few dollars should never be a justification to be content with second best.

Since I have torn down several engines and rebuilt them, I have a few stories of what the insides of engines look like. I've got a great one that deals with carbon and conventional oil!

 

Why do I use synthetics? It's pretty simple. I like knowing that the oil I use is not the weakest link in the system. I like the added stress I can put on the engine and still not have to worry about the oil breaking down. I like knowing that my base stock oil that gets injected into the engine won't evaporate before it all burns off leaving the additives behind as unburned deposits. I like knowing that my synthetic has a higher flash point than it's evaporation point which helps to prevent this. Of course this also has to do with formulation but I know the synthetic that I use is good. I also only truly endorse 1 oil. Actually 2. I endorse 1 conventional and 1 synthetic and will only use those 2. The extra cost is minimal for this piece of mind and really only adds up to less than half a tank of gas in terms of money over several thousand miles. A few dollars should never be a justification to be content with second best.

 

The manual says sythetic oil because it cracks the seals. The rotary is a unique engine and it has less of a compression. Using sythetic on a piston good on rotary bad simple.

 

I don't know much about blowby on a rotory but I would bet it's higher then a piston motor.

The typical piston motor pumps about a pound of unburned hydrocarbons in the oil about every 1000 miles. about 80" of those are volitiles that boil off. About 1% of that is tar, or roughly 5 grams. The other 19% that stays behind isn't exactly what I would call a good lubricant.

No matter wht the claims are about the composition of the oil new, by 3000 miles it's time to change - it ain't the same stuff that came out of the bottle.

 

What manual was that? The Hot Wheels car manual? Sure wasn't the RX-8 manual.

 

The RX-8 has a higher compression ratio than most piston engines.

 

It doesn't say any such thing as none of that is true. You made that up. I'm calling this bluff.

 

It's about average anymore.

 

to kind...

he is talking out of his ***...

beers