Make that 3 votes. Vinegar will take off the water spots on metal or glass. I had some water spots on the windshield of my 31 Tudor. Tried everything I could think of, no use. Someone suggested using white vinegar with a soft cloth. They just disappeared, been using white vinegar ever since.
Love the Waltons too but if you want to see Model A's and other brands of vehicles of the 30's check out Wind at my Back. It's on INSP, (Inspirational Channel). You can see many old cars on almost every episode. I love it and watch every chance I get.
One thing no one mentioned. If there is enough sludge in the oilpan itself to displace a half quart or whatever amount then all bets are off and all calculations are keput.