I hope you guys can help me figure out afew questions I have on the Rx-8's Oil system, I just have knowledge on Piston/Pushrod Engines..

1. Does anyone know where I can find info on how the Oiling System works for the RX-8.

2. During the summer will running 10-30 or 10-40 weight oil work better to keep the Rotors cooler or will the heavier weight Oil hurt , I want this to last and I'am looking for the best way to achieve this..

3. Everytime you change the oil & filter we are only replacing 3.7 quarts of oil , Are we looking for trouble down the road because of the remaining oil that's in the double oil coolers.

4. Does the way the RX-8 use oil differ a great deal from Piston/Pushrod Engines and does that mean the RX-8 oil Does'nt get as dirty as the Piston/Pushrod Engine.

I'am very New to the Rotary , So I need the help of the most experienced on this subject, which is probably everyone except Me...

 

1. TrussvilleMazda.com has a parts section. You can buy a shop manual there. I suppose you can learn alot there if you know how to read it. I'm sure some members can probably enlighten you a lot, also.

2. I've not heard of anyone using 10wAnything. Mazda USA suggests 5w20, and I was told by Mazda techs that 5w30 would be OK. I think the JDM '8s use a different weight, but I don't remember what it is. Run a search and you might find it. If not, Japan8 would probably know and might mention it later anyway (if he reads this thread). My theory: Better to be safe than sorry. The 5w20 was recommended, so it should offer sufficient cooling. Also, remember that oil is actually put into the chambers to lubricate the walls for the apex seals. This might influence you to get a lighter weight oil as it, theoretically, might make it a little tougher for the rotors to spin. I don't know how much of an effect it will have. Some people make a big deal about it. I don't know if I would. But, I've never tried anything other than 5w20/30.

3. I change my oil every 3,000 miles to make up for the stuff that stays in the oil coolers. I figure that should at least keep the dirty oil to a minimum, rather than letting the extra build up over a full 7,000 recommended miles. I think alot of other people follow this rule, also.

4. Yes, it's different (for example see above mentioned apex seal note). You'll see when you do the research or someone else tells you. You can (maybe) try howstuffworks.com: how a rotary engine works. Eventually, http://www.rotaryengineillustrated.com will have more info on that, too.

 

Here's my take:
1. Shop manual.\
2. I don't think the heavier oil will help. A heavier oil will flow less volume at a given pressure. Oil flow is key for removing heat, so I'd stick with the 5w20 or 5w30 to keep the flow rate up. In addition, the metering jets used to inject the oil into the rotor chambers is designed for a given weight oil (to get the desired volume of oil into the chamber). Again, I think its best to stick with the recommended weight of oil.
3. I've found that if I let the oil drain for 5 minutes with the car basically level, I usually will get a little more than 4 qts out. The remaining oil basically mixes with the new, so the percentage of old oil isn't that bad.
4. The main difference is that oil is purposely injected into the rotor chambers to lubricate the apex seals - so the engine uses oil by design. Another difference is that the oil is an important part of the cooling equations. And finally, there are far fewer bearing surfaces in this engine compared to even a 4 cyl piston engine. There are basically a couple of eccentric shaft journals/bearings, and a few fixed/rotating gears that guide the rotors around the trochiod chamber. That's it for the moving/bearing surfaces. No rod bearings, wrist pins, cam bearings/lobes, lifters/followers, valve guides, etc. In my mind, this means that the oil isn't subject to as much physical abuse (although the thermal abuse is probably a bit worse than a typical piston engine). So, I don't think the oil gets as dirty, and I think todays oil is easily capable of withstanding the temperature. For these reasons, I'm very comfortable with the 5000 mile oil change interval - following Mazda's severe-duty maintenence schedule.