oil leaking

you have to jack it up and look with a flash light. By the rear of the engine, do you mean towards the rear of the vehicle? The rear of an engine is where it connects to the transmission, in which case, it would be the main seal. You need to pull out the transmission to fix that one. Other wise, i could be the valve cover, head gasket or pan gasket. there's only one way to tell, you gotta look till you find it.