This is a post-mortem of the RX8 engine that I used do own. The failure was side seals. The failure mechanism was lack of lubrication. Mileage at failure was just under 50K miles. This was an AT vehicle with a 7500 rpm redline. The following are my thoughts on why it happened.
Mazda is balancing emissions with adequate lubrication in the Renesis. It is my opinion, as well as others, that emissions won and lubrication suffered. The motors that are lasting beyond 50K miles are the ST units with 9500 rpm redline. The oiling map is much enriched above 4-5K rpm. Those that run their ST units above 5K regularly are getting more oil to the seals from the oil injection pump. This running above 5K is more difficult for those with the AT.
Mazda placed two oil injection ports in each rotor side plate to lubricate the seals. These are ports, not long slots, so getting oil to all corners of the seals is, in my opinion, the job of fuel. Fuel is the carrier of the lubrication oil, just like in a 2-stroke motorcycle or chain saw motor. The rotary runs very rich, so there is lots of fuel to carry the oil.
The ideal solution to oiling in the rotary is to block off the sump intake to the oil injection pump and supply the oil injection pump with 2-stroke injection oil. This is what racers and those who use the rotary in aviation do.
In my opinion, this is why Mazda recommends “conventional” oil in the Renesis crankcase. “Conventional” oil has more grp I and grp II components. These oils are somewhat miscible in gas, leading to more oil in the far corners of the side seals in the Renesis.
The above is only an opinion on my part, but my own experience follows this reasoning. OCI on this car was no longer than 3K miles. Most of the early OCI’s were on Havoline and Motorcraft 5W20. My motor started to run poorly with two OCI of Royal Purple 5W20 that I used on the advice of “experts” at the RX8Club forum. My motor failed completely with the next OCI of Renewable Lubricants Inc. 5W20 that I used on the advice of another expert. The RP and the RLI are known to resist fuel dilution. I have no question that my motor would have failed anyway, as this is the experience of most of the owners of 2004 RX8’s with automatic transmissions. The use of synthetic oil just hastened its demise IMHO.
Anyone else have theories on this issue?
Mazda is balancing emissions with adequate lubrication in the Renesis. It is my opinion, as well as others, that emissions won and lubrication suffered. The motors that are lasting beyond 50K miles are the ST units with 9500 rpm redline. The oiling map is much enriched above 4-5K rpm. Those that run their ST units above 5K regularly are getting more oil to the seals from the oil injection pump. This running above 5K is more difficult for those with the AT.
Mazda placed two oil injection ports in each rotor side plate to lubricate the seals. These are ports, not long slots, so getting oil to all corners of the seals is, in my opinion, the job of fuel. Fuel is the carrier of the lubrication oil, just like in a 2-stroke motorcycle or chain saw motor. The rotary runs very rich, so there is lots of fuel to carry the oil.
The ideal solution to oiling in the rotary is to block off the sump intake to the oil injection pump and supply the oil injection pump with 2-stroke injection oil. This is what racers and those who use the rotary in aviation do.
In my opinion, this is why Mazda recommends “conventional” oil in the Renesis crankcase. “Conventional” oil has more grp I and grp II components. These oils are somewhat miscible in gas, leading to more oil in the far corners of the side seals in the Renesis.
The above is only an opinion on my part, but my own experience follows this reasoning. OCI on this car was no longer than 3K miles. Most of the early OCI’s were on Havoline and Motorcraft 5W20. My motor started to run poorly with two OCI of Royal Purple 5W20 that I used on the advice of “experts” at the RX8Club forum. My motor failed completely with the next OCI of Renewable Lubricants Inc. 5W20 that I used on the advice of another expert. The RP and the RLI are known to resist fuel dilution. I have no question that my motor would have failed anyway, as this is the experience of most of the owners of 2004 RX8’s with automatic transmissions. The use of synthetic oil just hastened its demise IMHO.
Anyone else have theories on this issue?