Should you use detergent or non detergent oil in a 1948 Ford flathead engine?

Answer 1

I've been using, experimentally at first, Mobil 1 synthetic with great results so far in a restored '40 Ford 2 door. I got the idea from a friend of mine with four Packards in his collection...the oldest being a '48 and the newest a 1956 Carribean Convertible. He's been a mechanic on fire equipment for over twenty-five years and said I'd have no trouble as long as the motor was fresh. He uses Mobil one in all his cars and says he would not use anything else in a new motor. The older oils were parrafin based, or so I'm told,and helped seal a "loose" or worn motor. Adding a new style oil will clean all the wax away and will PROBABLY lead to oil burning or blow-by. I say PROBABLY because I used it in an old flathead (already using oil) as an experiment, and the oil usage started to increase with the synthetic.

Almost all oils are detergent nowadays. This just means that the dirt and dust from intake and combustion is held in suspension by the oil instead of being deposited on the surfaces of the engine. This obviously has its advantages. If you are concerned about leakage, high mileage oils have "seal conditioners" in them to help prevent and treat leaks. I personally cannot comment about their efficacy though.