1988 2.5 t oil leaking from turbo

The PCV valve is under the intake on the left (drivers side) above the block. It looks like this.
Its hard to give a proper diagnosis without photos of the leak. The best thing to do is to clean up the area as much as possible and run it till it leaks. Then you should be able to see where its coming from.

5W30 maybe synthetic your choice, filter Fram XG9688 or equivalent , 5.81 US quarts of oil.
link below may help, press the helpful button
Oil Filter Change Hyundai Sonata 2011 SE 2 0T Turbo

some mechanics remove the hose going to the cooler tank and run the engine at idle till oil stops running. I like to remove the oil pan, clean it and fit a new filter.

are you hearing and strange hissing sounds ? check breather pipes all round look for any damaged pipes. some times squeezing them, also check the breather for the auto box.. on auto box clean all the road muck off and then go for a drive and then check it, look all round. do these checks. if nothing is damaged or leaking then you need to check the sensor. it could be clocked up and might just need cleaning. switch is located next to the oil filter. original colour is yellow if replaced it will be black color.

How long is a piece of string ? without a good look under the bonnet i couldnt say but make sure the engine breather is clean and not clogged as this would cause a build up of back pressure which will cause the oil top leak from everywhere possible

Maybe the sensor is bad...?

If You Had replaced The Seal After That Also Oil Leakage Is Occur, Then It Is a Problem Of BAck Compression Please Check It. thanks.

There's not much over there that can leak except for the filter. That diesel oil is heavy and persistent too. It'll drip from those steering linkages forever after a filter change. Check your turbo fittings too. It gets oil and then sends it back to the motor.

There are a few different things that will cause you to destroy turbos. It is very important that when you change the turbo you also change the mesh filter inside of the banjo bolt in the oil feed line to the turbo. This filter tends to get filled with sludge if you are not changing the oil enough, using poor quality oil, or if your turbo has gone bad, metal get stuck in this filter. Also make sure there is no metal pieces left in the oil feed line or any where else in the system.

You may also want to look into getting a turbo timer. This will give the turbo adequate time to cool down after driving, reducing the chance of warping the turbo.

maybe the front seal is bad