Well...I'm curious. You say that you end up with "black spatters all over the chain stays, seat stays and my pannier".
Is there a reason I haven't caught onto that you think it's coming from the chain? Chains don't...generally spray oil everything, unless you rub them directly against something. Even if it's raining.
I just bought a new car (a hatchback) with a light interior. I'm very careful to put the bike in with the chain side up. Still - it's already got quite a few black, greasy marks on it. In places that I could not have possibly fit the chain. You what they're from?
Bike tires. The road is covered in grit. Cars leak oil on the road, stuff gets dropped on the road...it's a mess. Once it starts raining, all that stuff get mixed up in the water. You wheel goes through the water and throws it up onto the bike, or in my case even when it's not raining it sticks to the tire.
I almost wouldn't have believed it myself, but I've seen my tires mark up carpet, car interior...without even riding in the rain, and in ways that couldn't possibly have come from the chain.
I think the best solution to your problem isn't a different chain oil, you need fenders. Even full coverage fenders aren't perfect, but - that's why commuters use fenders. It's often not to avoid getting wet - if it's raining fenders aren't going to help. It's to avoid getting covered in the nasty, gritty water that's kicked up from the street.