GG, the tolerance I've been told previously for Lyco IO540's is 1qt per hour too.
"Minimum safe" oil quantity was 3 from what I can remember.
I've had one spew its oil out on me. Started at 9 and ended with about 2-2.5 quarts in I think around an hour of flight time, not much more or less. No abnormal indication from T&Ps, but then again they were old gauges that were typical GA and did funny things once in a while.
They have a reputation for being a tough engine
.
Externally, though unable to see from the cockpit, it was very evident that something was amiss; the oil on the plane at the end of the flight (last one for the day back at home base thankfully!) was insane, much more than what was considered "normal".
Never was told the real reason why it did that, but I found out that I was blamed for it behind my back. If the so-called "chief engineer" said that in front of me he would more than likely have a few less teeth today...
Took a while but it did get fixed..... after the company pulling me in particular off the plane and continuing to run the machine with a box of oil in the back topping it up almost every stop.
All I can say is thank f*k I had two noisemakers........