I put in 7 with an oil change
For an oil change I start with 7 quarts... it shows about 6 1/3 on the dipstick; then add a quart when it drops to around 5.
Generally, it seems to take around 15-20 hours for the first quart then around 10 for the second and third... then, it's about time for the next change.
I am averaging 40 tach hours between changes.
RV7 powered by a lycoming thunderbolt IO-390
turning a whirlwind HRT prop
flying with more than 1,700 on the hobbs