Which oil should I use in my Model A?

[scar]

I'm sure this has been asked a million times, but i couldn't find a post on it.
I just bought a 1928 Model A last weekend.
I am wanting to change the oil but don't know what to use.
I don't know if the engine has ever been rebuilt or not. If it has, it's more
than likely been a long time ago.
I've read that Mobil 1 is a good oil, but I've read conflicting stories about
whether to use synthetic or non-synthetic, detergent or non-detergent, and which weight to use.