Greetings everyone,

In case anyone is looking into installing an oil catch can or has done so, I would like to talk about my experience and to ask for other opinions on people who messed with these things.

So, in autumn last year I have installed an oil catch can due to the engine oil breather shooting massive amounts of oil into the intake.

Reading about it, I did see few negative opinions claiming that, in turbo diesels an oil catch can can lead to turbo failures due to the circuit being more restricted (basically, the simple hose was to be replaced with about 1m hose with the catch can and the filters within it). If the crankcase was not relieved properly of pressure, this could force the turbo seals and they would go much faster.

Keeping this in mind, I bought the largest diameter "in" and "out" catch can I could find, with a slight filtration system already in it since I didn't want to mess with wire wools. I installed it and all seamed find, no smoke, no noises, it soon started filling with oil.

Through the winter and all towards the spring I emptied a massive 2 liters of oil in total for about 6000 km driving. The record build up was a full can (350 ml) in 5 days of city driving in temperatures about -10 degrees Celsius and about 150 km total driving. Inside was not even just oil but this thick sludge.

Then came spring and my turbo exploded, literally. Now, it is very important to note that the turbo was already whistleing on cold starts for about 2 years before. A year before it went it started to whistle while hot as well (that typical noise when it is not getting enough oil and it on it's way out). So the catch can was mounted when the turbo was already running poorly. How much, if at all, was this a factor in the turbo exploding? I have literally no idea.

After refurbishing the turbo, the shop where the procedure was done removed my oil catch can. Their take was that it is a non-standard feature and they don't recommend it. I could keep it but I would get no warranty for the turbo in that case.

Since I noticed that in warm weather the catch can gets very little oil anyway, (I got about 200 ml out in 2000 km - about 20% city driving in temperatures around 20 degrees Celsius) I decided to leave it out for the summer so I could have the turbo warray.

Now, just today I decided to reinstall it since I asked a few more local mechanics and all of them recommended using it as long as I am careful enough to empty it.

This time, after installing it I fired up IMPA and I went on a ride looking at Actual/Nominal values. There I saw something I was really not expecting. Turbo was running under the desired values, by about 200 units, mostly throughout the entire rev range.

Again, no noises or smoke, care felt like it was pulling perfectly, all seamed fine just like before.

I quickly removed it and put a standard hose, to see if the catch can was the problem and the values went back to normal. Desired / Actual was bang on perfect.

So, this was my experience and this is where I am now. Where I hope to get some second opinions are around these 3 scenarios:

1. Is a catch can recommended for this engine that spills massive amounts of oil into the intake through the oil breather (also noting that BMW has had issues with the original design and updated it to the vortex type afterwards that I would think is less efficient but doesn't block ventilation). Is that turbo value in IMPA something that can be ignored?

2. Is a catch can a bad idea for this engine and/or in general? Why would it be?

3. Only specific type of catch cans are recommended for this engine and/or special installation methods are needed, something that I may have not taken into consideration.

Sorry for the long post and thank you for taking the time.