Brownish Oil

After all that, I sure hope you got a good price on the car. Unfortunately, at least around here (Chi. 'burbs) so many ultimate driving machine drivers are FAR from ultimate drivers.
One more thing that can cause “milky” or as I like to call it “baby s**t yellow” is a clogged PCV system. Condensation settles with the lack of air movement thru the c’case. as posted above with short trips.
My wife hates it, but I taste the oil. Try a little new oil on the tip of your tongue, then do the same with the oil on your dipstick. You’ll be able to taste whether there’s gas dilution or anti freeze in it.