Desirable and acceptable are usually different values. For myself I've accelerated an overhaul decision when consumption exceeded a quart in 4 hours. But that engine was generally tired at the time. My current engine uses about a quart in 25 hours. I like that much better.
That's pretty much what I get in my Beech Sport. Normal cruse is 2400-2450rpm. I also use 7 quarts for and oil change. I try to fly at least 1 hour per week.
SI 1427B:
maximum allowable oil consumption limits for all Textron Lycoming
aircraft engines
can be determined by using the following formula:
.006 x BHP x 4 / 7.4 = Qt./Hr.