I realize I am just tossing another bit of unproven opinion into this thread but I would think that since rotaries burn oil more then a piston engine you want an oil that will burn clean and not leave deposits? Most oils are designed to resist burning and are full of detergents/additives but pure mineral oil, Like Rotella from Shell... burns clean. Thats what I use.

 

Gah. What do you type for the guy bangind his head on the wall?
Seriously, though, I think the cleanest burning dino juice is GTX. There was a chart with the residue from burning different oils, and AMSoil and royal purple actually burned the cleanest. I really wish I could find that chart. I think Icemark posted it way back.
From the faqs:
Can I use synthetic oils in my Rotary engined car?
Yes and no. Mazda offically 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, and will generally result in a 1 to 2% horsepower gain. However use of poor quality synthetics (like Valvoline, Castrol Syntec, Havoline, Etc) will result in build up due to high ash content left from these oils when they are burned. It is believed that is why Mazda did not recommend synthetics, because the couldn't pick favorites.
Edit: I found at least a portion of that chart in another thread:

Brand VI Flash Pour %ash %zinc

20W-50
AMSOIL 136 482 -38 <.5 ---
Castrol GTX 122 440 -15 .85 .12

 

hmm, i chose to post my point of view but never went into personal attacks...

 

Very interesting. I would like to see a full chart of deposits left by all the different modern oils.

 

Do a web search for "oil faq".
I have an older version mirrored here:
http://fc3spro.com/TECH/MODS/ENGINE/OIL/oilfaq.html


-Ted

 

I'll bring up a point that would have at some time come up since it has in the past when we talk about oil. Oil/fuel dillution. We all know it happens since our oil comes out with a heavily gas smell or take the filler cap off and you can smell it. David Canitz at RP was offering free oil testing back when the big list was the only source for info for people who just changed their oil, then after 1 to 3k miles, re tested to see the fuel dillution. David worked at RP, still does as far as I know. Some cars were showing 10% dillution. The synthetic oil uers dillution was about the same but the oil properties itself were less effected by the gas being mixed in with it. I'll have to search on the archives of the big list and try to find his e-mails concerning the subject.

Tim

 

Thanks, Ted, I've been looking for that for a while. Never thought to look on your site, though.

 

I think way back when I had my first rotary (79 GS) I read on the yawpower or felix Miata list about Rotella from Shell. Its got the low ash content. that stuff is supposed to be the best to use in a rotary because of the low 'buildup' of soot and ash . A lot of Diesel specific oils are formulated for low ash content. I would think they are best to use, and they are conventional dino oil so u can change the fast. I can find the 4 quart container at the Autozone for about 9-10 bucks.

I think its like 15w40 good stuff.

 

I think you can cut down your oil change interval in half and still come out ahead with your wallet in terms of cost over synths...

Oh BTW, Shell Rotella-T 15W40 user for over 5 years now!


-Ted

 

^ sweet I'm not the only one Can I get some props?

 

Oil is oil its all the same. "shakes head no. no its not"
There is a differance from say 0w20 and 5w20 as the viscosity sheering is higher.

As all things you ushaly get what you pay for. Oil is only changed because it gets contaminated. Try changing your filter more often or run duel filters.

My car and engins are worth good oil if you dont value your stuff then do what you want.

I never notice much if any changes runing RP over castrol GTX in my car but I know without a doubt what it is is doing and what bettor.

I noticed the bigest improvments in my bikes. Unbelivable improvments actualy. No more clunky gear box less grinding smoother clutch more controlable bike now. False inputs effect riding less fals inputs = go faster.

use what you want but my seasond input is stay away from Penzoil and Quakerstate and $1.50 oil. Redline and RP for me these days and GTX in my lawnmower.

 

i have had good luck with royal purple and runs much better and is noticeable in a turbo car.

 

Royal purple? Hell, just use Mobil 1 (15,000 mile formula) and forget about it for a year....(other than a few top-offs to make up for oil lost through the metering pump). You'll get the same results with Mobil 1 as you will with RP and change the oil much less often.

 

Penzoil creates sludge in the engine

 

Define "noticeable"?
Does it run cooler?
How much cooler?
What kinda temp gauge?
Oil is running cooler or water temps are running cooler?

Less vibration?
More power?

Come on, don't leave us hanging...


-Ted

 

I didnt read all the posts so i dont know if anyone has mentoned this yet... butt...


the whole idea behind synthetic oil is that it doesnt break down as fast as conventional oils. it takes the best parts of mineral, vegetable, and animal oils and combines them.

normal oil needs to be changed because the molecular structure of the oil gets pounded from cycling through the motor, and the oils vicosity is lost, aswell as its ability to lubricate and seal.

normal oil needs to be changed every 3000 miles. syntheic oil only needs to be chnged every 10 or 15000 miles.

the catch is, just becuase your new oils molecular structure doesnt break down doesnt mean the engines combustion cycle isnt going to contaminate the engine with carbon. the filter must stiill be changed every 3000 miles, but you can leave the oil in.

synthetic oil also cleans the engine much, much, much more better than mineral oil

it should save you money in the long run...

15000 miles = 5 conventional oil changes. lets say 25 bucks per oil change (20 for oil, 5 for filter) thats 125 bucks.

lets say the synthetic is 3 times more at 15 bucks a litre, so that 60 bucks lasts you 15000 miles, plus the 5 filters = 25 bucks....

85 bucks versus 125.hurah for synthetic.

if it makes you feel any better, jet turbine oil is 50 dollars for one quart, and theyll hold 10 or 20 quarts, and burn a quart ever 10 hours

for some reason I still run castrol gtx....

im done blabbering now.

 

Do you really think people would lengthen the service intervals like that?


I'd like to hear basis of proof for that.
This is the first time I've heard of this advantage.


-Ted

 

im talking from an airplane standpoint, the tolerances in a/c piston engines are a lot looser so they generate lot more crud

aparently its actually quite risky to switch from mineral to synthetic oil midway through an engines life. the synthetic cleans so well that you'll get a sudden builup of crud in your oil that could clog oil journals or do other damage

 

Are you saying that you use the same oils in airplanes?
Or are you implying data from oils used in airplanes are applicable in this discussion with rotary engines in automotive vehicles?


-Ted

 

Heh

 

Ok, my 2 cents on the synthetic thing.

Its worth it for 2 reasons:
wear and tear
gas mileage

i ran regular castrol in my Acura Legend for 1 year and took my average fuel mileage per tank/fillup frequently. Then i switched to mobil 1. I did more fillup averages and found that i gained 1.4 mpg. My dad did the same thing in his turbo volvo. He gained 1.6mpg.

But what about the extra cost of the oil? Well, i figured that i can bump my oil change interval from 3k to 5k. Then i figured the cost of oil changes and the savings in mpg. It works out to a savings of 72.48 per 5000 miles.

There you go, actual proof that it works. I wouldnt have beleived it if i hadnt tried it. Technology is your friend, and so is synthetic oil.

 

2 things.

1. What you have with your mpg gains is correlation, not causation. You can't truly say the increase was due to the oil.

2. You say you use synthetics for better wear and tear resistance. Now, do you think there will be less/more/same wear and tear from going another 2000 miles between oil changes?

 

wow...i didnt think this thread was gona blow up like this

on the point about oil i have noticed the temp is less than what it used to be. before it was a little under half and now it is even lower(under normal driving conditions) and it feels like it runs a whole lot better.

before as i accelerated it was kind of a rough feel but now it is just clean and smooth. after this i might try mobil 1 just because where i am no one carries it and i have to order it from racing beat(5.50 a quart) but the shipping is where they make up for it.

 

yes ted, piston powered aircraft use the same oil a rotary powered auto does. a/c oil just costs 4x more, just like everyhing else

 

I heard in another post that synthetic isn't the stuff to use in my rex because of the rotary?
And can I use airplane oil in my rex?