Rotaryspeed18, why do you change your oil at 1500 miles? And on top of that, use synthetic? Seems very, very wasteful...
But like someone asked before, trying to go 10,000 miles or more on even the best synthetic is bad for the engine - rotary engines let a lot of gas get into the oil, and this fuel cuts viscosity dramatically. To stay in spec, a 5W30 fresh oil need to behave like a 10W20 when it is used, at the end of its life. With fuel into it, this happens much earlier in rotary engines (none of us know when, hence many use heavier grades, like 10W40, that will not drop bellow a 10W20 during its life in the engine).
RG, indeed, carbon relates to the fuel. But, one purpose of the oil is to clean those deposits away, so different oils do make a difference (because they endup in the combustion chamber anyway). This cleaning is made by the detergents in the oil, and those are completely non dependent on the base stock nature (dino or synth).
RG, methanol is actually responsible for corrosion to metal parts and some rubber gaskets (those need a bit of aromatic solvent to swell and seal), but no deposits are observed because of it.
Poor quality gas (which does NOT mean low octane!) is responsible for sludge (soft, rubbery-gummy deposits) in the crankcase or combustion chamber/exhaust ports. Those have been seen in RX8 engines, on the ports. But before you jump to the conclusion and decide that synthetic oils have nothing to do with sludge, know that the earlier synthetics had a big problem with it. Because they are more pure than dino and miss aromatic compounds, those early synthetics could not keep sludge from accumulating. Nowdays, the veteran synthetics contain alkylated aromatics in their formulation, to make their solvency on par with dino oils and pass the sludge tests.
In conclusion, chose a well known synthetic brand that was around at least 10 years (as they would not be at their first formulation which might have problems). Only use oils with ILSAC, ACEA or API ratings. To be on the safe side, go one grade higher, or according to the climate and season of where you live (TX in summer = 10W40 would be my choice). Don't go much more than 5000 miles on a change if synthetic, or 3000 if dino (4000 miles if a blend).
I know there might be owners that bought a large case of 5W20 and stick with it by default, year long. At least for the summer month, do in June an oil change to 10W40, to last July and August. Use the large case for the other 3 seasons ;o)

PS Just in case - though supposedly compatible, it is safer to mix oils (even of different grades) from the same brand, if you must mix them. You could mix 2 qt. 5W20 with 2 qt. 10W40 to get through the summer with a 10W30 blend and still use some of the large case you got at a bargain price. The oil added between changes is better to be heavier grade, to balance the loss viscosity at high temp due to fuel dilution.
PPS the above mileages do not apply if racing - you're on your own ;o)
PPPS due to higher temperatures on 4ATs with one oil cooler, the use of a higher grade than 5W20 is almost a requirement.

 

I've been using syntech since my 8 is new and never had any problem. Took the car to the dealer for the engine recal. 55000 miles in my 8 and the engine starts like the first time I ran it. so no complains here abouit the syntech oils.

PS
Never exceed more than 3000 miles.

 

SYNTH AND DINO!!! PEOPLE YOUVE GOT IT ALL WRONG!!! BEER IS THE BEST LUBE FOR YOUR CAR! jk synth on mine 35k+

 

You can preach to me all you want but that still doesn't change the fact that synth is not bad for the engine and doesn't leave more deposits. I don't care about what synth did 30 years ago. That's irrelevant today. Want to compare a Model T engine technology to todays engiens too? Gasoline is also the #1 cause of deposits in the combustion chamber not oil.

 

We need synthetic gasoline, then!

 

The problem with synthetic gasoline is that it does not burn in the combustion chamber!

 

It burns - and even more cleanly than regular gasoline.
The problem is, some brands contain additives that are not rotary friendly (so, Mazda will not endorse any of it) and it costs 3 times as much as dino gasoline.

 

I'm making the rounds with my little Racing Beat book so here goes on their tech tips on synthetic oil for the RX8.

Syhthetic oils & the Rotary Engine by Racing Beat:
"One question we received often is, "Can you use synthetic oil in a rotary engine?" The official word from Mazda is that they do not recommend the use of synthetic oils in their rotary engines - specifically addressing this issue in the "Owners Manual."

In 1979 Racing Beat began testing Amsoil synthetic lubrication products. Without a doubt, synthetic oils do perform well in extreme heat (over 300F) and extreme cold (below 32F), but by nature of Mazda's rotary engine, the oil temperature never exceeds 250F without severe engine damage due to other factors. In Southern California, we have difficulty seeing the low-temperature benefits: however, when we put synthetic lubricants in the engine, transmission, and differential in our IMSA GTU race car, we immediately saw what we later found to be a common result: The oil temperature in all three locations dropped 5 to 10 degrees F for the same operating condition. This is apparently due to two factors: reduced friction between sliding surfaces, and reduced foaming. As we continued to use synthetic oil products it became clear that they genuinely reduced wear.

In the late 90's, we tested Royal Purple Synthetic oil. In the very first test, this oil added more than 1% HP on a highly developed race engine. Since then, we have been using Royal Purple Synthetic Oils and have seen similar improvements and more in other applications, along with low wear and reduced operating temperatures.

We have noted 3 concerns with synthetic oils: 1)higher cost vs. mineral based oils; 2) the fact that it inhibits break-in (so use mineral based oils; during break-in period); 3) and the fact that there is the potential for problems if you change to synthetic oil after years of using mineral oil in an older rotary engine. These problems are two-fold. First, synthetics sometimes cause rubber seals to swell after years of immersion in mineral oil and second, synthetics tend to be high-detergent by their nature, so changing to synthetics after many years of mineral oil use can cause beneficial sealing carbon deposits to be scoured away, leading to higher oil consumption. We believe that these are some of the reason that Mazda does not recommend synthetics - even though their race teams have used them!"

 

That last bit sounds like advice from the Reagan era...

 

Watch it there Bub. They named an airport, a library, a highway, a fire hydrant, and at least 200 star wars installations after him...

 

Not to mention the DC Trade Center building.

 

Yeah I can't speak to the particulars of which engine or which synth oil they are speaking to at the end with the disclaimer. It's enough for me to switch over after I am done breaking in engine #2. Man I think I'll need to buy stock in Castrol after all the money I'm about to start spending with them between sythetic oil and pre-mixing...

 

I'm not sure if this has been mentioned before but I was in the dealership and picked up a bottle of the "Mazda Rotary Oil". On the back label it said:

"NOTE: Synthetic or Synthetic blended oils are not suitable for Pre-Renesis Rotary Engines."

Seems Mazda says its OK for synths in our Renesis? Confused...

 

Really ? Mind to take a picture of the bottle and share it with us ?

 

I think he is talking about Mazda Dexelia Ultra 5w30 Can't get it in the USA

 

Isn't the Dexelia oil a synthetic blend?

 

Depends on which chemist you ask. Dexelia has been mentioned in this thread before. Use the "Search this thread" feature for Dexelia to see the older posts.

 

It definitely didnt seem to be Dexelia oil to me? It said on the front of the bottle "Mazda Rotary Motor Oil API SL 5W30". I didn't take a pic of the front of the bottle but I did of the back, more so that I would remember how to type the aformentioned quote. The picture is on my phone - I'll upload it tonight if you guys wish. It did read on the back (only):

"Mazda genuine Rotary Motor Oil is a mineral based oil which has been approved by Mazda Australia Pty. Limited for use in all Mazda Rotary Engines.

NOTE: Synthetic or Synthetic blended oils are not suitable for Pre-Renesis Rotary Engines."

Thanks

 

pre renesis,

what does that mean??? i would go with it means before renesis..

so... there is your sign..


beers

 

Yeah thats what I'm saying. Firstly the product is a mineral oil for a rotary yet mentions synthetics are no good "pre-renesis". Thats what makes it confusing!

 

i read it the other way.. as in syn did not work in the motors 10 years ago..

long story.

but then again your flashes are not the same as ours.. who knows... i premix with syn.. but i am a silly guy..

beers

 

Yeah I have to say that I dont read it as an endorsement of synthetics in the renesis, purely that you shouldnt use them in pre-renesis engines. The absence of the information doesnt mean its an endorsement.

I have a MRO bottle at home. I am giong to head off now and take pic if you're interested.

Cheers

Andrew

 

Bugger, looks like I threw it out, but here is a shot of what the front looks like https://www.rx8club.com/attachment.p...1&d=1181970850

Is that what you had?

 

Yep, Mazda Rotary Motor Oil. To quote from Mazda's AU site

Does Mazda have a recommended Oil for use in it's vehicles?

Mazda recommends the use of Mazda's Full Synthetic, "Premium Motor Oil" API SL 5W-40 Motor Oil in all it's Petrol and Diesel Engine vehicles and Mazda "Rotary API SL 5W-30" oil for all Rotary engine vehicles. This oil is also available in convenient 1ltr quantities for use when topping-up the oil in Rotary vehicles.

 

Sorry to bring the dead thread back.. I agree with rotary god. Gas quality would affect as much as oil quality.. I used synthetics on my FDs for several years. Even when my coolant seal went out and my PFC read 124+C water temp, I drove 200+ miles back to my home just watching the oil temp. When the engines broken down, It had some carbon build up, but hard to say if its because of oil.. But everything else (inside rotor, e shaft, etc looked good). I used Mobile 1.

Now, I just switched to conventional oil just because the cost issue and didn't see much benefit... as I change 1500 miles on my FD.

But those of you who's concerned about synthetic oil injection, I know FD there is an adaptor in which you could inject 2 cycle instead. I'm going that route on my FD that I'm building and run full 100% Mobile 1

Also, people need to realize, driving habits could result more in carbon build up. And also, the RB statement about rubber seal deterioration.. who knows.. If Mazda uses cheap seals that can't even handle that, I would be VERY surprised.. As during winter time, most gas uses EtOH in which harms more than some additive in oil.. Again, I think we are looking too much into this..