[swamp2]

Jason has shared one detail: Approximately 17,700 folks report some form M3 in the "drives" field. I asked if there was any attempt to discern if this includes all generations of the M3, but have not heard back on that yet. It seems quite safe to conclude this is all series of M3s since the total US production quantity is about 30k and there is pretty well no way over half of all E9X M3 owners are forum members.

Can we do any better for an estimation of a failure rate with this data? Maybe just a bit.

1. This site caters to E9X M3 folks, there are no dedicated sections to the other series except a relatively small subsection of the E9X section for E46 M3.
2. There were very roughly the same number of E46 M3 made as E9X M3, actually a few more E46, but roughly equivalent.
3. It's probably safe to say that a very high percentage of members here would post about something as tragic as a total catastrophic engine failure.
4. To get a conservative failure rate, upper bound, we want to have the denominator (or relevant pool) as small as possible.

So let's assume half of this 17.7k number are E9X owners. Some are simply lying and others own some other series of M3. Let's also assume only half of these folks would report an engine failure. This gives us a total pool of about 4.5k folks. With 22 failures we arrive at just a bit under 0.5%.

No matter how much we try to squeeze the denominator down we still have a worst case scenario failure rate of half that of the E46 M3. And that is not even apples to apples since we assumed 100% reporting of failures in the E46 M3 case, which we know absolutely is not realistic, especially back in those days of the "primitive" internet...

Again, it is abundantly clear that this is nothing like the E46 case. There is an overall quite low risk of failure somewhere between about 0.1% and 0.5%