The maximum oil consumption on my engine (O-360-A1A) is .78 quarts per hour - per Lycoming. That is a quart of oil every 1.3 hours. This number is for airframers when selecting an engine for their airplanes - Cessna, Piper, Beechcraft,……. and you (since you are the airframer). The goal here is to not let oil consumption to be the limiting limitation on range as advertised by the airframer. At .78 qts/hr, my 8 Qt oil sump, with a 2 Qt minimum safe limit should last 7.6 hours. This (in most cases) exceeds the fuel quantity range limit on most certified GA airplanes. Does Lycoming think you should be flying around with only 2 quarts of oil? I don’t think so, but you can safely do it if your other primary oil limitations (pressure and temperature) are within limits. Do they recommend filling the oil sump to 8 quarts? I don’t think they would recommend that either. But they built their sump to hold enough oil so that max range at max oil consumption would exceed max range of the airframe at normal fuel consumption. That’s how they sell engines to Cessna, etc. They don’t sell an engine to Cessna, they sell a fleet. It’s a big deal.
How does that affect what we do? We are the airframer, and even if we didn’t build it, we can dictate the way we operated our engines. We decide how much oil we are willing to add to the crankcase when we change the oil, and how low we are willing to let it go. Lycoming’s minimum RECOMMENDATION (for us EAB guys) is 2 quarts, maybe more for you, if we choose to comply with that recommendation. Personally, I put in 7 quarts during an oil change, because nothing pukes out at that level in my airplane as long as I’m not inverted. When my oil level drops below 5 quarts, I add one unless I’m getting close to an oil change, and then I don’t. I typically change my oil every 25-35 hours, and don’t need to add any between oil changes.