kyoo

Hello, please read:

I've done some searching regarding this topic and posted in other threads as well but did not get any response. Basically,

Synthetic is better in every way period EXCEPT for it's burn off characteristics, which is more or less only an issue for Mazda's rotaries since they're designed to inject oil into the motor, correct? With the exception being that Idemitsu oil, which I'm assuming was designed particularly with that burn off characteristic in mind.

I guess my question is - has anything changed since most of these older threads <'05 were made? I guess what I'm more interested in is any changes in design to the 13b-rew since the car left the states, particularly 99+ specifically in regards to oiling?

Or, is there a running list of "good burning" synethetics? ie, I always use Amsoil in the Evo, mainly for the ZDDP, which is good for the motor/turbo. I'd like to consider the longevity of the turbos for the rx7, while at the same time making sure I'm using an oil that will not leave residue in the motor. Frankly, it's a little annoying that the motor was designed this way in the first place.

Aaron Cake

iTrader: (1)

You can run synthetic oil if you want. This has been covered very extensively. Basically, the original recommendation from Mazda not to run synthetic is based upon one or two brands at the time which may have left deposits. Not an issue today.

However one must consider the added cost of synthetics, in an engine designed to burn oil which may or may not have a hundred thousand miles on it already.

Me personally, I save the synthetics for the drivetrain and use whatever oil is on sale in the engine.

kyoo

Thanks for the response - I'm always running amsoil in the evo, so I don't mind the added cost. Is there any documentation about the burn characteristics of synthetic oil today, or the recommended brands? I never imagined that to be something that synthetic oil developers strived to achieve, unless it was for a 2-stroke motor.

Is it common knowledge here as well about Mobil 1 dropping a class in the quality of their oil?

Evil Aviator

All of the major brands of synthetic seem to work fine in a rotary now. Amsoil, Idemitsu, Red Line, and Royal Purple claim that their products work with rotary engines, and there is no evidence to prove otherwise. Rotary engine compatibility is usually addressed in the FAQ of the respective oil website. Even though not recommended by the manufacturer, people have used other major brand synthetic oils like Valvoline and Mobil 1 with no reported problems. However, most people still use non-synthetic engine oil for break-in.

The rotary engine causes a lot of oil shear, so most synthetic oil vendors do not recommend extending the oil change interval. As far as I know, only Royal Purple recommends an extended drain interval, and honestly I'm not sure if this is such a good idea.

The added cost issue is due to the fact that synthetic engine oil does not usually offer enough benefits to justify the higher price for a simple street car. Also, a rotary engine consumes at least 1 qt of oil every 3,000 miles as part of its normal operation. Like Aaron Cake, I only use synthetic oil in the transmission and differential. The rotary engine works great with Castrol GTX.

As for ZDDP, so far there is no evidence that it helps rotary engines.

Yes, and they are also known to refuse to answer any questions about what is actually in their oil, and their transmission oil is known to eat synchronizers.

Eduardo Santos

That's suspicious...

Now, about that thing of Mobil 1 dropping a class in the quality of their oil:
Has that been always like that, or was that a change that they made to their oils recently?
I was wondering, because I read this thread:
https://www.rx7club.com/showthread.p...05#post5131205
and it says:
«Can I use synthetic oils in my Rotary engined car?
Yes and no. Mazda officially does not recommend the use of synthetic oils in rotary engines, however, long term and racing use has shown that the better synthetics (Redline, Amsoil, Neo, Royal Purple, Mobil1) are perfectly fine to use in a rotary engine (...)»

So I was thinking that Mobil1 was a better quality oil than most of it's counterparts, but after reading what you wrote...

kyoo

gotcha - very clear post, thanks. i've been trying to find updated information but was having a hard time.

i used to have a dealer account for amsoil, so i know they like to push their product and synthetics in general as the best and only option, so it's hard to trust what they say, and evos hate royal purple for some reason, so it's good to have feedback by real rx7 owners.

Amsoil does have good protection against shear, but either way I still maintain early oil changes anyway. Like I said I don't really mind the extra cost - I'm more thinking about the turbos anyway. I am aware that up to 3k miles there is not too much difference between synthetic and conventional but I will still stick with synthetic for peace of mind, now that I can have it with rotaries.

Been away from Mobil 1 for a long time now.

thanks again

Evil Aviator

They may as well be politicians:
https://www.mobiloil.com/USA-English...Base_Oils.aspx

It changed about 10 years ago as far as I know. They were very sneaky about it.

I am not aware of anybody having any problems with Mobil 1 engine oil. However, it is now just a synthetic blend, so I don't see any point in buying it. I would rather save some money and use Castrol GTX for the street, and the far superior Red Line or Idemitsu for the track.

LOL, yes, but at least you know that Amsoil is good stuff made with real Group IV base stock, as is Royal Purple. I prefer Red Line because it is made from Group V and IV base stock, and it is usually priced lower than Idemitsu.

Eduardo Santos

I've read that article. Indeed, they really sound like politicians...

kyoo

yeah i am a big supporter of amsoil. never ran royal purple, like i said somehow the evos just don't run well with it - usually use red line for drivetrain fluids though

Jackygor

I had nothing but great results with amsoil.

Sgtblue

iTrader: (16)

Agreed. Other than I personally run synthetic for the turbos. I think their biggest advantage is performance in a high temperature enviroment. If I was n/a I wouldn't bother.

StormBeforeDawn

Dito on that. My 83 pushes to much to really go for the more expensive kinds. Whatever is on sale is good enough for me.

Gringo Grande

iTrader: (97)

Neo in the Drive Train...Walmart Synthetic in the engine.

Evil Aviator

Synthetic oil is also superior in low temperatures.

If your turbo is a modern water-cooled type such as the stock RX-7 turbos, then regular "turbo-approved" oil is just fine for street driving. Most of the motor oil on the shelf at your local store is rated for ILSAC GF-5 or API SN, which indicates that it is specially formulated for turbos. If you downgraded to an outdated aftermarket dry bearing turbo, then synthetic oil isn't such a bad idea. Just make sure it is real synthetic oil. As you can see from this NOACK volatility test (which is a factor for "turbo approved" oil), regular old Castrol GTX beats the fake synthetics:
http://www.syntheticoilreviews.com/n...lity-test.html

NEO is real synthetic oil, but Wal-Mart Super-Tech is fake synthetic oil. The FTC ruled that Group III hydrocracked oil could be marketed as "synthetic" even though it technically isn't. Yes, that's right, it may say "full synthetic" on the bottle, yet it is in no way synthetic oil. Gotta love it.

Jeff5808

iTrader: (7)

Castrol GTX is the only oil I put in any of my cars, aside for the drive train. I use Redline for that.

Sgtblue

iTrader: (16)

Maybe so. Admittedly it's anecdotal, when I removed my stock, original turbos with 90k (which had been getting synthetic) to do a rebuild for a failed coolant seal, I checked the oil lines. I found no evidence of coking which I understand is pretty common with conventional oil. Those same turbos are still on the car, very little shaft play, no smoking and boosting just fine at 115k now.....knocking on wood. No track, but alot of autocross events and street in the car's history.