The probability of a normally maintained and operated piston aircraft engine failing without warning is infinitessimal unless you mis-manage it or your fuel;
Just not true. Aircraft piston engines can and do fail through no fault of the pilot. It's rare, but not that rare. If you've been around aeroplanes for a few decades you'll know of many such incidents. I certainly do, including one such collection of whirling and reciprocating bits I was sitting behind.
how often has your mass-produced, poorly constructed car engine just stopped for no reason half-way through a trip? Never? Thought so.
Never? Don't be so presumptuous! Several times, actually, and not in old bangers, either. Cracked distributor cap (2 year old Beetle), snapped cam belt (Ford Cortina a few years old, belt well inside its swap date), failed coil pack (2 year old Omega), coolant pump failure (another quite new Omega), rupture of high pressure fuel injection line (scary - Cavalier). Probably others I have forgotten.
And bear in mind that an aircraft piston engine runs at much higher power settings for longer than any car engine does.
You are a lot safer in your SEP doing 200 miles over water than you would be sitting down the back of a nice big ETOPS aircraft which has just had an engine shutdown, and is starting a 420 minute single-engine diversion across the Southern Ocean with the crew hoping like hell that the other one holds up.
Bollox. The failure of a modern turbofan engine is hundreds of times less likely than a piston engine failure.