In the last 43 hours I've added 2 ounces of coolant. to the overflow thank. That 43 hours (over 5 months) included normal operation a mid-range, lowish, and even high-normal water and oil temperatures. As well as parked in hangar at just below freezing temps.
I haven't kept previous records of previous times in the 8 years of ownership that I've topped up coolant, but IIRR I've probably done something like that before in my ownership.
The question is basically "is this normal or even typical? Does it raise concerns?"
I can't find any obvious seepage at hose claps or cooling system cap or radiator., find no traces of coolant on hangar floor or inside lower cowl.. Though I did once find a tiny droplet of coolant on a wing spar.
If I added 2 ounces of coolant to my car radiator every 5 months, unless I could see/find a leak, or a radiator cap pressure test detected one, or the amount increased over time, I'd consider it "normal" seepage.
