Hi, one more story hoping that somebody with much more knowledge, expertise and experience can give me a hand.

I'm trying to chase above normal oil consumption.

1) I thought it was the twins. They were swapped for a good used set. The smoke under boost seemed to be gone, but oil is still somehow disappearing.

2) Found a leak on an oil return line, bolts seem on their way to strip. I am going to tackle that on Monday.

3) I noticed what follows: without getting on the boost, if I let the car run off throttle (I noticed this while going down a hill) and then get on it and generate some boost, there is a bit of smoke coming out of the tail pipe. But if I boost again right after, no smoke. I am getting the impression that the car sucks oil while under strong vacuum, then the boost clears it up and it stops smoking. I tried to boost it, put it on neutral, slow down, do another pull; no smoke this way. It gets better; while I noticed this situation this morning (BTW, after adding some oil), this afternoon, I tried to reproduce the symptoms, but no matter what I did, there was no smoke from the tail pipe. The smoke (when it was there) was clearly oil. The car pulls about 18+ vacuum at 8/900 rpm idle as soon as it settles when it is started cold. There is absolutely no coolant loss or smell. Some times (not every time I start her in the morning) there will be a very tiny bit of blue smoke as soon as the car comes on; this will disappear within a minute or less; it is very faint and sometimes I am not even sure whether it is actually blue or it is the usual white smoke I get when started cold.

Does anybody have any insight? I would really appreciate it. I have searched, I have found smoke under boost, smoke under deceleration, but not smoke after deceleration, the first time you boost, but not the next (say on the next gear). I am going to look at the primary elbow vacuum lines this weekend, I have read about the PCV and -forgive the non-expert question- where is it located, and is there anything I can do to test it without tearing the entire bay out? I believe I read that somebody has driven without the oil filler neck cap on to check for this... Is it OK to do that? Finally, my dipstick seems to be loose. It doesn't pop, out, I find it always in place, but it is not sealing. Could this be a problem or lead to any kind of problem?
BTW, I have capped the vacuum line on the oil filler neck (the one that can be capped).

I apologize for the long post. I tried to give the best picture possible. If you can help, I'd appreciate it.

 

no mention of amount of oil loss as shown by dipstick or the mileage taken to elicit the oil loss.

 

^ He's right. You need to tell us what you consider excessive oil consumption. How many many km or miles does it take for the dipstick to go from F to L?

Also, the PVC system, is just designed to vent blowby gasses either back into the UIM under vaccuum, or into the primary turbo intake under boost.

The valve itself is found in the vaccuum line that goes from the front of the UIM to the oil filler neck.

 

I apologize for omitting this detail.
Part of the reason why I did is because that is also something that doesn't necessarily happen constantly.

I used a tankful of gas and at the end the dipstick had gone down approximately 3.5 of those diamonds marked at one side of the stick.
There will be times when I drive a couple of days, say 150/200 kms and I'll see little change or hardly any. There will be other times when I'll drive 50/80 kms and see 2 diamonds drop.

Another thing you might want to know is my average driving style. I don't kill the car ever. I don't get on the secondary that often either. I am not saying I baby it, but a combination of time, roads around here, circumstances at the moment (need to install a boost controller and I am watching my pedal) and the fact that I'm trying to diagnose this issue, don't allow me to get on it constantly.

I usually warm her up, then start driving and I wait for at least 15/20 minutes since I fired her up (depending on outside temperatures) before I start getting on the boost. When I do, I usually pull around 4/5.5 K (at least recently) and for no longer than a couple of gears (because of roads and time available to me). This only takes place for a limited amount of time, as for the rest, I am pulling around 4K and doing short bursts of few seconds.
I hope this is enough information.

BTW, Castrol GTX 10W30 in the car.

 

check your oil metering injectors. in stock form they have a vacuum line that runs from them to the inlet on the front turbo (for filtered air). They have check valves inside them that can fail. when this happens under boost the oil will be pushed out into intake track, or onto the top of the engine if no vacuum line or a small filter is used.

See if you can suck air through the vacuum line on the oil metering injector, if you can, then the check valve is failed and you need new oil injectors.

 

Thank you, it was one of the things I was going to inspect. One silly question though: how do you avoid ingesting crap contained in the vacuum line, if there is any?