OIL? Isn't that one of the most dangerous things you can pour on the road? The reason there are so many accidents on the first day of rain is because oil goes to the top and causes lots of slippage. This is the first time I've heard of oil being sprayed on the roads. You may want to call the county on this one.
It's probably heavy oil and it's probably sticky. It's probably best to assume that in dry conditions it will get you dirty and make traction worse (but not all that bad, unless it liquid like plain motor oil. it wet conditions it probably does make traction substantially worse (you'll still be fine if you're extremely careful about turns and stops) and will get you even dirtier.