Air cooled aircraft engines can use fuel dilution to thin the oil in very cold weather. This makes starting possible in Alaska.
While, it's not "good" for the engine, it works well enough.
However, the aircraft engine oil is different from modern automotive oils (which are much thinner).
I'd guess the needle and seat are bad, possibly due to ethanol in the fuel. I'd replace them. Also consider a fuel shut off valve.
I'd also change the oil.