oils for rotaries (13b)

Not open for further replies.
Apr 12, 2003
Irvine or Berkeley, Ca
I was wondering what oils people suggest for roatries? Many of my freinds drive 2nd generation Rx-7's (turbo and non-turbo types) on track. I was wondering what oil they would benefit from. There are some warnings from Mazda about using synthetics, but it is a old warnign from sometime inthe 80's or early 90's. What would people suggest for a hard driven rotary?
I don't recall the exact details but mobil has stated that they have tested their oil on the Rotary Engine and found it to work well. They disagreed with Maxda. They did stare that they could not recommend it though bc it would run counter to Mazda's claims and would expose them to product liabilities. Go over to Mobil1.com or call the technical services dept at Mobil.
In my possession is a 1994 RX-7 owner's manual with very stern warnings against using synthetic oil. I don't know if the new RX-8 RENESIS rotary, which is a heavily modified 13B, has the same warnings. Mobil 1, Amsoil, and Red Line have all been used successfully with racing rotaries, but street use is a different story. You probably know that oil is metered into the fuel to lube the rotor apex seals. As I understand it, Mazda's concern with using synthetics in rotaries is that synthetic oils do not combust as conventional oils do, so ash builds up, causing detonation. The detergent and additive package in street oils is also an issue: racing oils don't typically use detergents, which also create ash when burned. Detonation will kill a rotary even quicker than it will a piston engine. Mazda went to the trouble of creating a special synthetic oil for its racing rotaries, including the 787B racer with the 26B four-rotor that won Le Mans in 1991. The chemistry of this oil is different from that of other automotive synthetics and is covered in SAE paper 922375, "The development of lubricating oils for rotary racing engines". (Unfortunately, as I key this, I don't have the paper handy or else I would have mentioned its base.) You can order a copy from SAE; its website is easy to find, and the organization doesn't mind dealing with the public. You can buy a street version of this special oil from Mazdaspeed at roughly $35 a liter (about a quart). Mazda did not want to use an existing synthetic oil for the grueling 24-hour Le Mans race, during which the car covered several thousand miles at speeds up to over 200 mph. There has to be a reason. If you use a synthetic oil in a rotary, be careful. I do wonder about one thing. Synthetics are far more common in Europe than here. What oil does Mazda recommend for its RX-7s and RX-8 there?
Just checked. The Mazdaspeed Rotary 1 synthetic oil for street use is polyalphaolefin based with a molybdenum friction reducer. At least one Internet source has it for $107 for a 4-liter can. My questions about Mazda's oil recommendations for rotaries sold in Europe still stand.
I love Mazdas warning concerning the FD3S. Note that the new RX8 doesn't have it, nor did any other RX7. How many engines did Mazda replace on the '93-95 RX7s? Enough to take a financial beating and pull the car from the market [LOL!] I doubt Mazda will make that mistake again(especially considering the underhood heat of twin turbos in the FD3S). The RX8 uses 5w20 motor oil here. There is no warning against synth. The USA RX8 uses dual oil coolers. From what I understand, Jspec/Aus/Euro RX8 use a single oil cooler. And, these other market vehicles can use 30 and 40wt oils.
Yea I know about the oil metering in rotaries, I would think it would be safe to assume that synthetic oil would be ok if one was to block it off and run pre-mix. So it would be ok for my friends to run Mobil 1 and Redline when they drive the car hard (I doubt any of my friends are willing to spend $100 for an oil change!). It does make sense though that Mazda would develop a specfic oil for the 787B, after all it is Le Mans [Smile] . So what weights and types of synthetic oil would you reccomend, or should they just go with dino? I thought the FD was taken out of the US market for emissions reasons (13b TT and OBD 2 don't like each other) and slow sales. Although there were many replaced engines and turbos when there shoudln't have been (dealerships didn;t know how to work on them and mess up simple problems like a loose vaccum hose, another big problem with them).
I'm a wee bit confused about the problem (I'm confused about a lot these days). If the synthetics don't burn as well as mineral oil does, than I guess that they will be lubricating all the way to the exhause port. Have read some anecdotal stuff about synthetics making harder, more tenacious deposits, that could be part of the alleged issue. I'd guess that additives would be the big issue with these oil injected systems.
Wouldn't the higher number of detergent (calcium right?) addatives in Synthetics be better for cleaning out the carbon and whatnot? I'm wondering if this has to do with the high flashpoint of Synthetics, but sholdn't combustion reach a much higher temperature than the flashpoint of any oil?
Quote from Patman
I wonder if a group 3 "synthetic" would be a good match for a rotary perhaps?
I was wondering the same thing. I believe one of the advantages of group III base oils is that they burn cleanly and don't leave much in the way of deposits. Perhaps a group III oil that does not have a very high TBN (less than 10) would work well in an older rotary engine. [I dont know] [ November 04, 2003, 06:44 AM: Message edited by: Sin City ]
Not open for further replies.