This is an unusual and rather expensive oil that many BITOG folks may find interesting to read about.
Mazda worked with Idemitsu Kosan Co., Ltd., to create a special synthetic oil for its racing rotaries, specifically the 900-hp 26B 4-rotor used in the 787B racer that won the Le Mans 24-hour race in 1991. Under the rules in effect then, that was the last year the rotary was eligible for competition in the class of cars that was likely to win the race outright, as opposed to winning just in a particular class. However, I must note that any 24-hour high-speed race is grueling, and just to finish Le Mans at all is an accomplishment. On the long straight, speeds of well over 200 mph (320 km/h) are usual.
The racing oil is described in detail in SAE paper 922375 of 1992, "The development of lubricating oils for rotary racing engines" by Takao Yabe et al. of Idemitsu Kosan. This paper is available from SAE.org and is well worth reading in full. Considerations in developing oil for the 26B included minimizing what the paper calls "spitback", which is leakage of combusting fuel-air mixture past an apex seal that is sticking because of oil-related deposits, and minimizing fuel consumption.
Mineral oils were out because they and their detergent inhibitor (DI) package created the problem deposits. Against mineral oil, Idemitsu Kosan tested polyol ester (PES), polyalphaolefin (PAO), and 3 different blends of polybutene (PB) synthetic oils. PB had advantages in minimizing deposits, hence the emphasis on PB variants, but in the end the company decided to use PAO for thermal stability and high viscosity index. Extreme pressure (EP) additives were considered but rejected in favor of small amounts of a DI package meeting API SG specs (which were current in 1991). A moly compound was added as a friction modifier. To minimize bearing wear required a viscosity of SAE 40.
In 1996 Mazdaspeed, which is Mazda's factory performance outfit, released a street version of the oil as "Rotary 1" in 10W40 viscosity meeting API SH (then the current spec). It came in rectangular 1-liter and 4-liter metal cans painted in the same green and orange colors as the 787B Le Mans winner.
The Mazdaspeed news release of 3 June 1996 said that Rotary 1 is "tuned to suit road cars" and "can be used in all MAZDA rotary engines (non-leaded hi-octane or regular gas versions)". This raises interesting questions concerning Mazda's long-standing warnings against using synthetics in its rotary engines in North America, though I understand from other BITOG posts that the RX-8 seems not to have this same prohibition. The release said that advantages of using Rotary 1 included minimizing "sludge" (carbon) formation and creating a more stable film for the seals.
Mazdaspeed list prices in 1999 were US$38 for the 1-liter can and $133 for the 4-liter can. Right now, though, Corksport.com in Oregon lists the 4-liter can for $107, which works out to $26.75 per liter.
Hope you enjoyed this. One question that I think would be interesting to answer is this: why not polyisobutylene (PIB)? Another firm tested PIB as an alternative synthetic oil in rotary engines and reported promising results in an SAE paper in 1971. Anyone heard of any recent applications of PIB oils?--Ed, the rotary guru (so I've been called)
Mazda worked with Idemitsu Kosan Co., Ltd., to create a special synthetic oil for its racing rotaries, specifically the 900-hp 26B 4-rotor used in the 787B racer that won the Le Mans 24-hour race in 1991. Under the rules in effect then, that was the last year the rotary was eligible for competition in the class of cars that was likely to win the race outright, as opposed to winning just in a particular class. However, I must note that any 24-hour high-speed race is grueling, and just to finish Le Mans at all is an accomplishment. On the long straight, speeds of well over 200 mph (320 km/h) are usual.
The racing oil is described in detail in SAE paper 922375 of 1992, "The development of lubricating oils for rotary racing engines" by Takao Yabe et al. of Idemitsu Kosan. This paper is available from SAE.org and is well worth reading in full. Considerations in developing oil for the 26B included minimizing what the paper calls "spitback", which is leakage of combusting fuel-air mixture past an apex seal that is sticking because of oil-related deposits, and minimizing fuel consumption.
Mineral oils were out because they and their detergent inhibitor (DI) package created the problem deposits. Against mineral oil, Idemitsu Kosan tested polyol ester (PES), polyalphaolefin (PAO), and 3 different blends of polybutene (PB) synthetic oils. PB had advantages in minimizing deposits, hence the emphasis on PB variants, but in the end the company decided to use PAO for thermal stability and high viscosity index. Extreme pressure (EP) additives were considered but rejected in favor of small amounts of a DI package meeting API SG specs (which were current in 1991). A moly compound was added as a friction modifier. To minimize bearing wear required a viscosity of SAE 40.
In 1996 Mazdaspeed, which is Mazda's factory performance outfit, released a street version of the oil as "Rotary 1" in 10W40 viscosity meeting API SH (then the current spec). It came in rectangular 1-liter and 4-liter metal cans painted in the same green and orange colors as the 787B Le Mans winner.
The Mazdaspeed news release of 3 June 1996 said that Rotary 1 is "tuned to suit road cars" and "can be used in all MAZDA rotary engines (non-leaded hi-octane or regular gas versions)". This raises interesting questions concerning Mazda's long-standing warnings against using synthetics in its rotary engines in North America, though I understand from other BITOG posts that the RX-8 seems not to have this same prohibition. The release said that advantages of using Rotary 1 included minimizing "sludge" (carbon) formation and creating a more stable film for the seals.
Mazdaspeed list prices in 1999 were US$38 for the 1-liter can and $133 for the 4-liter can. Right now, though, Corksport.com in Oregon lists the 4-liter can for $107, which works out to $26.75 per liter.
Hope you enjoyed this. One question that I think would be interesting to answer is this: why not polyisobutylene (PIB)? Another firm tested PIB as an alternative synthetic oil in rotary engines and reported promising results in an SAE paper in 1971. Anyone heard of any recent applications of PIB oils?--Ed, the rotary guru (so I've been called)
