The Engine Failure Story
RX-8 engines don't have a very good reputation. Unfortuantely, the reputation is well deserved. Fortunately, the general public at large has it ALL WRONG, while at the same time as generally being right.
Back in 2004-2005, reports of RX-8 engine failure started to pop up, alarm was generated, and the reputation was born that these engines don't last 30,000 miles. Part of this was that engines were actually failing. The early ECU flashes weren't injecting enough oil, and things were wearing out fast and/or breaking. MSP16 was the final iteration to try to solve this. However, this was only part of the problem. MOST of the initial problem was simple mis-diagnosis. Owners would feel misfires or power loss, they would change their spark plugs, and the problem wouldn't go away. They would take it to the dealer, who would poke around trying to find a problem, and not finding one, decide that the engine needed replacement. They would order an engine, put it in the customer's car, and send them on their way. It wasn't until years later that dealers started realizing that the IGNITION COILS were failing around 30,000 miles. There are no hard numbers, but many of us (not all of us) believe that a large portion of the original "engine failures" were nothing more than simple ignition coil failure, and were replaced needlessly.
Mazda created their own remanufacturing plant in 2008 to take over the process directly, and the Caterpillar contract was canceled. It is not known if the quality control issues were the reason for the canceling of the contract, or if it was just a temporary contract from the beginning. Quality improved with the new plant, however there are still quality issues, mostly around variable seal clearances and too much sealant being used inside the engine (which leads to cooling system failure)
This is how many of the original 2004s and 2005s went through multiple engines. Replace something that isn't broken with something that is and yeah, things aren't going to go well. Reman quality is significant better than it was, but certainly not perfect still.
Now, if you remove those problems from consideration (the original ECU flash and the reman quality problems), then the engine is very reliable. There are still several major design flaws that tend to hurt the lifespan of the engine, and there are other failure methods where you can destroy a perfectly good engineREALLY fast through in-attention. Most RX-8s DO get a 2nd engine within 100,000 miles, so yes, engines are replaced all the time, but not for the reasons that the general public likes to believe.
+ How many are replaced?
Well, that is still mostly guess work and theory, though there is some indication from outside sources and leaked Mazda information that around 50% of RX-8s have had at least 1 engine replacement in it's lifespan. There is an interesting article in this thread that goes into some detail on the reman facility's engine build volume: RX8Club.com: Article gives insight into just how many RX-8 engines have been rebuilt
+ How about the newer RX-8s though? Shouldn't they be good to go?
In 2009 they introduced some subtle but significant engine changes correcting several things, the most critical of which was an increase in oil pressure to RX-7 ranges (they dropped it for the 2004-2008 years for some reason), and re-introducing the center oil injector (they deleted it for the 2004-2008 RX-8s for some reason, all prior rotories had the center injector). This doesn't make them immune to engine failure however, for example a failed thermostat could kill a perfectly good engine, but it helped to reduce the wear-related failures a bit.
A compression test should be standard before anyone buys an 8 though, just to be on the safe side. Most dealers charge $120 to $250 to do a compression test. I go more into the compression test here.
+ So why do these engines have such a poor outlook?
The problem is that there are so many different ways for an engine to fail:
- Excessive carbon buildup accelerates seal wear, causing compression loss (particularly a problem in automatic RX-8s)
- Excessive carbon buildup unseats the seals, causing compression loss (particularly a problem in automatic RX-8s)
- Excessive carbon buildup causes the seals to stick, causing compression loss (particularly a problem in automatic RX-8s)
- Excessive coolant temperatures cause coolant seal failure (particularly a problem with older RX-8s that haven't had a cooling system overhaul)
- Excessive heat buildup warps the housings to one degree or another, preventing the seals from sealing, causing compression loss (particularly a problem with older RX-8s that haven't had a cooling system overhaul)
- Excessive exhaust temperatures overheat the side seal springs, warping them until the side seal pops out of it's location, clips the exhaust port and shatters, throwing shrapnel through the engine (particularly motors that are turbocharged, supercharged, or see nearly 100% track time)
- Fuel pump failure or high lateral G left turns with low fuel causes fuel starvation under load, creating a lean spike that causes detonation and shatters seals (particularly a problem with older RX-8s that haven't had a fuel pump replacement)
- Cat failure (even more common than engine failure) causes localized heat and pressure buildup that overstresses the seals and breaks down oil viscosity, leading to various issues (particularly a problem with new owners that don't know to replace their ignition)
- Clogged oil injection lines prevent oil from being injected, leading to excessive apex seal wear and side seal overheating, leading to compression loss and/or catastrophic failure (particularly a problem with long oil change intervals)
- Subpar reman engine quality, starting with low compression that accelerates any other issue (reman quality has improved over the years, but bad apples are still reported)
These are just the common failure methods. There are uncommon ones, and/or freak ones, like a transmission issue snapped one guy's e-shaft somehow (probably a defective e-shaft that was too weak), or issues that are entirely owner caused, like too low octane or not keeping on top of the oil level.
Any single preventative measure you can find only addresses at best a couple of these, maybe just one method, and maybe none at all (but people think it does). And since you don't usually know how well the engine was put together in the first place, it's largely a roll of the dice on these engines.
Short answer: If possible engine failure makes you that uncomfortable and/or paranoid, then this is NOT the car for you. You have to accept the issues or ownership will turn into a nightmare. It still could anyway, but your mindset going in is far more important than statistics. The more prepared you are, financially and mentally, the less of a problem any of this will actually be for you.
Yes, I paint a bleak picture. However, it really isn't much worse than any other sports car. Every sports car out there has had it's share of problems. Why do we still love the RX-8 anyway? We love it because of it's ability to plaster a grin on your face. More on that later.