The engine failure story:
Most of the engine failures were on 2004s with automatic transmissions. The 2004s in general had more issues due to the flash not adding enough oil and a few other things off the boat, and the automatics being 4-port and usually driven much more casually compounded the problem.

Compounding THAT was the original reman facility for the engine replacements did not have very good quality control, and alot of those original reman engines had improper seal clearances and other build issues that caused quite a few people to get to their 3rd or 4th engines.

MSP-16 updated the flash and improved things greatly, and happened early 2005. Mazda North America can tell you if MSP-16 was performed for any 2004 or 2005 if you give them the VIN. they also re-vamped their reman facility, and reman engines 2006+ are now usually far better than the original factory ones. So if you find a 2004, 2005, or 2006 with an engine replacement that occured late 2006 or later, don't take the engine replacement as a negative mark against the vehicle, but a positive one, as it means the engine is likely in fantastic shape, and good for quite a long time.

Plenty of 2004s were still perfectly fine.

2005s have a much reduced failure rate, 2006 further, 2007 and 2008 are relatively rare.

In 2009 they introduced further 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 it).

A compression test should be standard before anyone buys an 8 though, just to be on the safe side. Most dealers charge $80 to $120 to do a compression test. I go more into the compression test itself in a post further down.

You might be wondering why it is that we 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
- Excessive carbon buildup unseats the apex seals, causing compression loss
- Excessive heat buildup warps the housings to one degree or another, preventing the apex seals from sealing, causing compression loss
- 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 (usually race motors, possible but rare in street motors)
- 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
- 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
- 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 (depending on which fails first)
- 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.