1989 supra turbo
 

My supra has an oil hose that is connected next to where I fill my oil. It is leaking but I don't know what this hose is called or what it does. Please advise. Thanks

You posted this in the wrong section... I'll move it to the MKIII forum.

That's the crankcase breather hose it vents excess crankcase pressure to the head where it is then pulled out via the PCV system. It's critical but it's not an oil supply line.