if it is brake fluid your brake cylinder is bad if it is gear oil you have a bad axel seal
Axle seals
It is not the brakes leaking oil , Its the axel seals leaking rear end gear oil. If its not gear oil , Then its brake fluid and that means wheel cylinders are leaking.
Leaking brake cylinder (or caliper piston if it has rear disc brakes). Also if its a rear wheel drive vehicle it could be differential oil leaking from the outer axle seal. If its a brake fluid loss you can monitor the fluid level in the master cylinder .
your main oil seal on the rear of engine is leaking or the timing cover seal is leaking,
NO. You either have a rear main oil seal leaking or the back of the intake leaking oil and even could be a valve cover gasket leaking. But I would say the rear main is leaking and when the engine is running the flywheel slings oil onto the starter.
Make sure it isn't leaking from above and running down. Such as a front or rear main leak.
You probably have a bad front or rear oil seal.
Rear main seal leaking? Valve cover gasket leaking? When engine attains normal operating temperature the motor oil will thin out and will possibly leak, where thicker (colder) oil will not.
It may have water in the rear diff or over filled the oil. Drain the rear and refill. Hopefully you get just oil.
If it is red fluid leaking, then you have a transmission leak. If it is oil then the rear main oil seal is leaking on the back of the engine. You need to look at the top back part of the engine to make sure the back of the intake is not leaking oil, check back corners of the valve covers for leaks too. Need to make sure the oil sending unit that is back beside the distributor is not leaking oil. Ruel these things out before you tackle the rear main oil seal.
Water can not leak from the rear main seal, only oil. Most likely there is a leaking freeze plug near the rear main seal dripping water onto it.
Valve cover? Engine seal/ front or rear?