not talking about running without oil or anything like that. Regular oil changes, kept topped up, etc.; but the engine failed due to a lubrication failure? Statistically these days, it just doesn't happen, without regard to what the oil used is (ignoring extremes).

Is anyone aware of a published, controlled test in which a modern engine saw empirical service benefit from synthetic oil? Perhaps it can be proven that increased service intervals are possible, but I have not seen even that test, let alone one that could claim, let's say, improved reliability.

Having said all that, I use synthetic oil in the gas cars and normal Rotella in all the diesels I own.