Mazda Rotary Oil Question

Messages
11
Location
Virginia
I have a new Mazda rx-8 rotary just about due for its first oil change. It is not my first rotary (I've had 2 other rotary cars and 1 motorcycle) There is a real debate about synthetic oil useage in rotaries with a lot of strong opinions on both sides. I have used Amsoil for decades in my nonrotary vehicles and personally believe it is the best oil available. I never used it in my rotaries due to financial (oil use) issues. The owner's manual stipulates 5w20 oil. There does not seem to be an abundance of choices. I have decided on motorcraft 5w20 - a product with Ford's name on it (a part owner of Mazda). The oil is supposed to be a blend of synthetic and dino oils. Does anyone think that would be an issue with this engine?
 
Messages
263
Location
San Diego, CA
Reading about the "non burning synths", isn't that a 'good thing' in this case? If they don't burn up, they will be left to lubricate, right? Not that i'm recommending synthetics, just trying to spin it the other way. If a lube doesn't burn, it won't leave behind any residue to clog the rings. ferb!
 
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47,835
Location
Everson WA - Pacific NW USA
First of all I'm not sure where this thing started about synthetic oil not burning or not burning cleanly. Sure synthetic oil, especially polyolester based synthetic will stand up to heat much better than petroleum refined oil, but it will still burn. Second, the oil base has nothing to do with "ash", well unless it has lots of sulfur or other non-oxidizable stuff in it. But synthetics have less sulfur, that's for sure so the "unburnables" will come from the additive package. Simply put synthetics are LESS likely to foul plugs etc. Look at synthetic 2-stroke oils. Think about the oil groups. Think about a group III oil base for example. More or less problems? It's not really a synthetic, but it's more than a simple cracked hydrocarbon. Will it "burn" more cleanly? Your choice for oil, but follow your owner's manual. I'm no rotary engine expert, but let's stick with the facts.
 
Messages
34,394
Location
NJ
Drew, good post. I'd use Pennzoil 10w-30 in this car and change it every 3-5k miles.
 

TC

Messages
1,644
Location
California
"The RX-8 manual states only 5w20 SL or ILSAC oils...no mention is made of not using synthetic oil." That pretty much says it all, plus there's warranty compliance to concern yourself with. I'd interpret your owner's manual literally in both what it says and doesn't say. Any 5w-20 SL oil is appropriate in your car, regardless of it's composition. So the matter breaks down to the universal "which brand is best" conundrum. P.S. Cool wheels! [Smile]
 
Messages
3,593
Location
Outside smalltown, IL
classicred - Nice car. A buddy of mine got one of the first ones in Illinois. Call me the odd man out here. I'd run Motocraft 5W-20 in the car. It satisfies the warranty requirements and so far we've yet to see a bad UOA with it in a piston engine... [ November 22, 2003, 11:51 PM: Message edited by: jsharp ]
 
Messages
9,448
Location
USA
Does the owners manul preclude the use of synthetics? Early RX-7 owners manuals said in plain print not to use synthetic oil! Seeing how so many oils are partialy synthetic today it almost seems impossable not to get some synthetic compounds in the oil! I would imagine that it is not forbidden by the owners manul the most important issues for the oil would be shear stability and low ash! TO be real honest with you if I felt compelled to run a 20wt I would only run Redline! Here is why we know that Redline is not going to shear badky like most oils when exposed to that oil injection system. We know it will take the high heat and that it will be able to clean without sacrificeing it's lubricateing property's. THe early wankles were very hard on oil and ran rather dirty!
 
Messages
335
Location
Colorado
I wouldn't run anything less than a 10w-30 oil in your car. Don't fall for this 5w-20 crap that Mazda throws at you in order to squeeze a couple of mpgs for their CAFE (corporate average fuel economy). This renesis engine is still a rotary and rotary's need high oil pressure and a thicker oil. Mazdatrix is a reputable source for rotary rebuilds, high performance mods, and aftermarket accessories. Here is what they say about synthetic use in a rotary: http://www.mazdatrix.com/faq/synthetc.htm The Rotary engine has an oil injection system that injects small amounts of oil into either the intake tract, carb, or rotor housing (depending on year/model). This is needed to lubricate the various internal seals and surfaces. The injected oil MUST BURN, and must burn clean. The root answer to the question is that not ALL synthetic oils burn, and not ALLof them burn clean. The ones that do not burn accumulate until they foul the spark plugs. The ones that do not burn clean can leave residues of various substances (like ash? plastic? non-organic sand?) that accumulate until the spark plugs foul, or a seal sticks -- could be apex seal, side seal, corner seal, or oil control ring. The normal consequence of a stuck seal is an engine tear down. In the many years we have been involved in rotary engines, we have NEVER had a problem with GOOD petroleum based oils. They work fine! They are less expensive than synthetics. (We use Castrol 20-50 GTX). They burn clean, etc. etc. The problem with answering the original question is that it is NOT a simple yes or no. We DO simplify it to a "NO", but that is because we do NOT know whether the specific brand of synthetic the customer has in mind will work. AND, if it does not work, how long will it be before the damage shows up, and how bad will the damage be? Maybe it will take 10,000 miles, maybe 50,000 miles?? Maybe the engine will fail due to something unrelated to the oil, and there won't be enough left to determine why the failure happened. WE are not willing to take that gamble, are you ? Then, take a minute to think of WHY you want to use a synthetic. If a rotary engine (properly maintained, oil changes at 3K intervals, etc.) can still be running fine at over 200,000 miles, the engine does not need any more cooling, the gas milage will not be any better, etc. etc. WHY do you want to spend more $$ and gamble on engine and/or spark plug damage? (If you are into the fossil fuel thing, pollution, depleting our resources, etc. then you should not be driving ANY car!) We are not chemists, and we do not have the time, $$'s, nor inclination to do 100K mile tests of various synthetics in rotary engines. We DO use synthetics in the transmissions and rear ends - it works fine.
 

classicred

Thread starter
Messages
11
Location
Virginia
John, The RX-8 manual states only 5w20 SL or ILSAC oils. In spite of the raging debate on the RX-8 forum, no mention is made of not using synthetic oil. However, if there is any question, why go to the additional expense of full synthetic oil? And redline costs even more that Amsoil. With shipping inclused, I pay about $5.02 a quaart for my 5w30 Amsoil. The crux of the arguement againt synthetics seems to be that it will not burn cleanly due to its higher flash point. As I'm sure you know, rotary engines inject oil into the chamber to lubricate the apex seals. It is claimed that the residue from incomplete combustion with foul the intake or exhaust ports, leading to reduced engine life. Of course, the new Renesis engine uses all side ports as opposed to the old peripheral exhaust ports on earlier designs. I don't know if any of this stuff is true or just opinion. Further, I know there is controversy about the need to use 5w20 oils as opposed to 5w30. What's a guy to do?
 
Messages
63
Location
Virginia
I had an RX7 and was brought up to not use synthetics in it. Rotary engines brun oil as part of their normal course of business & the synthetics don't burn as cleanly. Many Mazdas use Ford engines in them but the RX8 isn't one of them! As you point out, the Motorcraft 5W-20 is a synthetic blend. I'd recommend the Chevron Supreme 5W-20.
 
Messages
335
Location
Colorado
Synthetic oil in rotaries is a waste of money (assuming that they can be used in the first place, which I don't recommend anyway). Reduced cold starting wear and extended oil change intervals are the main benefits of synthetic oil. Neither of which really apply to a rotary. If you are going to do 3k oil changes in a rotary, why bother with a synthetic? Penzoil or Chevron 10w-30 will perform as well. BTW, there seems to be a problem with the side seal sealing on the renesis engine. Lots of premature engine failures/replacements due to coolant leaks. Mazda ownership by Ford is showing.... [LIST]
 
Messages
43,676
Location
'Stralia
I've always wondered about the "no synthetics in rotaries" issue. Given that Dino is more liekly to have bitumenous or heavy hydrocarbon traces, I'd have thought that type of base would leave more carbon. As previously staded, the additives are most of the ash/fouling anyway. Why don't Mazda have two separate oil supplies ? One with 2 cycle oil for the injection, and the normal sump for the barings and side seals.
 
Messages
1,412
Location
Falls Church VA
Following is based on acquaintance chatting with Mazda tech person some years back: Mazda found that some synthetic oils caused problems in rotary engines. Rather than mention any by name, company decision was to recommend against use of synthetics. Specifically, according to source, no problem existed with either AMSOIL or Mobil 1.. Another friend ran his RX-7 on AMSOIL for many years. After he passed it on to a kid, who was perennially short of cash, it was weaned to Mobil 1. Now with replaced engine, it is back on AMSOIL. Something in excess of 200,000 miles on it now (and I'm not saying that changing brands of oil had anything to do with the replacement of a tiring rotary engine).
 
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3,518
Location
Austin, TX MSA
quote:
Why don't Mazda have two separate oil supplies ? One with 2 cycle oil for the injection, and the normal sump for the barings and side seals.
many people have been known to do just that.
 
Messages
335
Location
Colorado
There is a vendor in the Florida panhandle that sells a conversion kit for the 13B that provides a separate oil reservor for the oil injection system. The reason why Mazda doesn't do this is because too many dumb owners would forget to check it and fill it on a regular basis. Look how many 13b's were destroyed because people didn't check and add oil to the crankcase between oil changes... Again, why waste the money with synthetic when you are going to do changes at the recommended 3k interval? Who cares if Mobil 1 or any other synthetic can withstand higher temps before oil breakdown-the engine seals will be long gone from overheating before the oil breaks down.
 
Messages
146
Location
Irvine or Berkeley, Ca
Many people pre-mix their rotaries for those reasons. Has anyone tried a fleet disel oil in their rotary? Delvac 1 would keep those combustion chambers clean. Also rotaries are cooled by oil in addition to the coolant. I would expect them to thin out their oil even with those huge oil coolers they have stock. Anyone know how the diesel oil does in a 13b?
 
Messages
43,676
Location
'Stralia
guys, leave it to me to invent an idea that has been used for ages. 00scrub, I think that that Delvac 1 wouldn't be good - ash, and a synthetic seems to go against all that's been posted so far.
 
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