The great Oil problem that plagues turbo disi

[SonofJoe]

Ah! Now I understand (I think?).

It sounds like the original problem with turbo leakage/smoking exhaust is NOT an oil related problem at all and simply a case of bad physics (if the boost is too high and the PCV system is undersized, then crankcase pressure increases, gravity draining of the oil in the turbo is compromised and the oil takes the only other path available to it which is out through the turbo seals). Would I be right in thinking that the original problem develops as the engine gets older? As the engine's piston rings wear and lose some of their tension, and top ring groove fouls, you will see a progressive increase in blow-by past the rings. This will only partially be accommodated by the PCV system (which itself might be restricted by oil deposits) and as a consequence, crankcase pressure rises.

In this case you can forget all of that stuff I said about seal face wear and seal groove deposits!

Okay, so you've swapped out your original turbo and you no longer have smoke in your exhaust. However I'm going to guess that your pistons will be seeing a lot of blow-by relative to the original engine design. I'm going to assume that that blow-by is also seriously hot which probably means your oil is going to get hot (120 to 130°C?) on long, spirited drives. In which case, I would be less concerned about stuff like wear and more concerned about oil volatility. You really don't want a conventional oil in your car because it's Noack volatility will be way to high. I would even go so far as to say conventional Group III synthetics are too volatile. My pick for your engine might be something like Amsoil 10W30. This is a PAO based oil with a very low Noack (4.1%). Such an oil would be very oxidatively stable (good for turbos in general) and minimise the risk of oil exiting the crankcase in your blow-by (oil loss isn't the concern but piston ring fouling from burnt oil is).

You could go down the Ester route. All things being equal, these oils have the lowest Noack of all the base oil groups and they have better resistance to oxidation that PAO. However they are incredibly expensive and I'd see if you could live with PAO before considering the jump to esters.

 

[JFAllen]

Originally Posted By: Haxir


Penz plat for natural asp? So what would you suggest for a disi turbo?


Depends on the turbo diesel? does it have a DPF? is it under warranty? is it a 20-cylinder 1.5MW CAT stationary engine?
Horses for courses. remember that small automotive diesels are much harder on oil than their industrial/marine counterparts. lots of time in traffic at idle, wide operating conditions vs 1500RPM for days on end.

To-SonofaJoe: The most typical cause of a smoking turbo is flogged bearings, leading flogged oil seals leading to increased shaft play, which cycles back around. This is typically brought on (initially) by dirty/gritty oil.) That's way most people who spend any time with turbocharged cars insist on 3000mile/5000kms oil changes with quality synthetics. Sadly it's also why most Japanese imports ahve flogged turbo's as the Japanese are natorious for poor car maintenance... More regular oil changes are significantly cheaper than turbocharger replacement

Some chap paid $2500AUD to replace the flogged out turbo on his Saab 9-5 as a result of Saab's engineering/oem maintenance requirement/oil specs not being accurate/appropriate. Sold the whole car to me 6 month later for $2900, and everything else is perfect on it. I cleaned the sump, and a bunch of other engine internals, now running Helix ultra ECT C3 (Dexos2) oil and have improved fuel economy by a measured 12%. Have also ensured I'm not going to have an oil starvation issue (it's a Saab thing.)

as an old avert once said. Oils ain't Oils.

Oils in petrol turbochargers must work in an incredibly harsh environment. Remember turbo's glow red hot, and there is oil right there cooling the whole show. Diesel exhaust's jsut don't get as hot, but they have higher bearing loads at low RPM.

The best defence against turbocharger failure is clean oil
even more important than expensive oil

you can take that to the bank.

Regards
Jordan

 

[Virtus_Probi]

I would suggest that M1 5W30 ESP is worth looking at. High HTHS for its grade, 3.58 with M1 0W40 being a 3.6 for comparison.
Low NOACK loss, around 6%.
Low calcium formulation to minimize LSPI concerns in the DIT engine.
Low SA, might minimize turbo deposits? Not sure about that one.
Only issues to my mind are cost and the need for frequent changes due to a low starting TBN.
FWIW!

 

[SonofJoe]

A couple of additional thoughts...

Although I never ran any specific turbo oil tests, from time to time, I'd have to run some tests which put oil through it's paces at temperatures which at the time seemed to me to be ludicrously high from a crankcase perspective.

There was a test you needed for Renault OEM approvals. I forget what it was called now but it required you to take a finished oil, spike it with a cocktail of oil soluble metal (to simulate the presence of wear metals), heat it up to about 175°C and sparge it with air for around 9 days (216 hours). At the end of the test you would test the oil for TBN depletion, TAN increase and most important of all, viscosity increase (this being the most obvious sign that control of oxidation has been lost). I'm guessing this was sort of intended to simulate conditions in a turbo.

Standard minerals & semi-synthetics always died a rapid death on this test however much you loaded them up with additives. The oils would be lucky if they got to 100 hours before they 'broke' and KV shot up at an exponential rate. On the other hand, PAO based oils were the dogs bollocks because of their superior resistance to high temperature oxidation. It also helped that generally speaking, they contained far less VII polymer (all VIIs hate heat). I can't speak for esters but my guess is they too would have done well.

Although these sorts of tests might nudge you towards thinking a 'proper' synthetic is what you need for a turbo application, it's not really that representative of what actually happens in the turbo. For starters, despite the v high temperatures you get in a turbo, there can't be that much oxidation occurring because there's almost no air present. You might be better served by a bona fide super high speed, high temperature bearing test.

Finally, it occurs to me that maybe we've got turbo lubrication all wrong. My first car (a Morris 1100) used the same engine oil for both the crankcase and the transmission. It was a dumb idea! Today it's the norm for the crankcase and gearbox to have separate oils. Maybe in 2017 it makes sense to decouple the turbo from the engine and let the turbo have it's own separate oil system. Maybe such systems could be filled for life with 'proper' high quality oil more attuned to the needs of the turbo as opposed to the needs of the crankcase?

 

[bigj_16]

Originally Posted By: JFAllen
Originally Posted By: Haxir


Penz plat for natural asp? So what would you suggest for a disi turbo?


Depends on the turbo diesel? does it have a DPF? is it under warranty? is it a 20-cylinder 1.5MW CAT stationary engine?
Horses for courses. remember that small automotive diesels are much harder on oil than their industrial/marine counterparts. lots of time in traffic at idle, wide operating conditions vs 1500RPM for days on end.

To-SonofaJoe: The most typical cause of a smoking turbo is flogged bearings, leading flogged oil seals leading to increased shaft play, which cycles back around. This is typically brought on (initially) by dirty/gritty oil.) That's way most people who spend any time with turbocharged cars insist on 3000mile/5000kms oil changes with quality synthetics. Sadly it's also why most Japanese imports ahve flogged turbo's as the Japanese are natorious for poor car maintenance... More regular oil changes are significantly cheaper than turbocharger replacement

Some chap paid $2500AUD to replace the flogged out turbo on his Saab 9-5 as a result of Saab's engineering/oem maintenance requirement/oil specs not being accurate/appropriate. Sold the whole car to me 6 month later for $2900, and everything else is perfect on it. I cleaned the sump, and a bunch of other engine internals, now running Helix ultra ECT C3 (Dexos2) oil and have improved fuel economy by a measured 12%. Have also ensured I'm not going to have an oil starvation issue (it's a Saab thing.)

as an old avert once said. Oils ain't Oils.

Oils in petrol turbochargers must work in an incredibly harsh environment. Remember turbo's glow red hot, and there is oil right there cooling the whole show. Diesel exhaust's jsut don't get as hot, but they have higher bearing loads at low RPM.

The best defence against turbocharger failure is clean oil
even more important than expensive oil

you can take that to the bank.

Regards
Jordan

I agree on all of this. Turbo bearings going bad, will drop the impeller, destroying the seals. If it goes too long, the impeller will drop right into the housing.
There are ways to use the existing oil in the engine, to address the turbo. In the EMD engines I am familiar with, they have a separate pump (turbo soakback) with its own filter that runs engine oil through the turbo for 30 minutes after shutdown

 

[MCompact]

I ran M1 5W-30 and 5W-30 EP in my 2007 MS3 for eight years and 158,000 miles.
Engine modifications consisted of a Mazdaspeed cold air intake and a mild Hypertech flash tune.
At 69,000 miles I switched from a 5,000 mile OCI to a 7,500 mile OCI.
At 123,000 miles I switched from M1 5W-30 to M1 5W-30 EP.
UOAs consistently confirmed that the engine was in great shape and that a 7,500 mile interval was conservative, if anything.

 

[4WD]

Probably less VM was used back in the day …:

 

[JFAllen]

20W50 Mineral oils are still widely available in Australia. For reasons unknown, both GM and Ford spec'd that grade of oil for there aussie built cars for years, despite the rest of the world using XW30W oils. To this day people use it in their modern cars (old habits die hard... don't we oil nerds know it.)

While they may or may not be significantly modified (VII or PPD's,) they have very low viscosity indices. Thus they're not especially stable with temperature. Get them much past 110C and they don't hold their viscosity well, but will most likely still be >3.5 HTHS at 150C°. Still not ideal for a highly strung turbo car. Good use cases are boat motors that labour hard for hours at moderate revs, but have excellent oil cooling.

Given how 'reactive' Grp-II oils are I often use 20W50 or 15W40 cheap mineral oils to do a sacrificial oil flush (while conducting regular maintenance.) When you've got a sludge prone turbo Saab, you learn to keep that oil crystal clean

Regards
Jordan

 

[K23Turbo]

You having a modified turbo engine, which automatically puts it in severe service. 3-5K oci on a full synthetic. For my 2.0 four cylinder turbo(single) engine, I usually run Amsoil. Or Red Line. I’ve good results with a Castrol Edge(black and gold). I vote
M1 HM 10W30
M1 EP 10W30
M1 0W40 Euro
CE 0W40 Euro(black)
CE EP 10W30
Amsoil 10W30(any Line)
Red Line 10W30

 

[Haxir]

Originally Posted By: SonofJoe
Ah! Now I understand (I think?).

It sounds like the original problem with turbo leakage/smoking exhaust is NOT an oil related problem at all and simply a case of bad physics (if the boost is too high and the PCV system is undersized, then crankcase pressure increases, gravity draining of the oil in the turbo is compromised and the oil takes the only other path available to it which is out through the turbo seals). Would I be right in thinking that the original problem develops as the engine gets older? As the engine's piston rings wear and lose some of their tension, and top ring groove fouls, you will see a progressive increase in blow-by past the rings. This will only partially be accommodated by the PCV system (which itself might be restricted by oil deposits) and as a consequence, crankcase pressure rises.

In this case you can forget all of that stuff I said about seal face wear and seal groove deposits!

Okay, so you've swapped out your original turbo and you no longer have smoke in your exhaust. However I'm going to guess that your pistons will be seeing a lot of blow-by relative to the original engine design. I'm going to assume that that blow-by is also seriously hot which probably means your oil is going to get hot (120 to 130°C?) on long, spirited drives. In which case, I would be less concerned about stuff like wear and more concerned about oil volatility. You really don't want a conventional oil in your car because it's Noack volatility will be way to high. I would even go so far as to say conventional Group III synthetics are too volatile. My pick for your engine might be something like Amsoil 10W30. This is a PAO based oil with a very low Noack (4.1%). Such an oil would be very oxidatively stable (good for turbos in general) and minimise the risk of oil exiting the crankcase in your blow-by (oil loss isn't the concern but piston ring fouling from burnt oil is).

You could go down the Ester route. All things being equal, these oils have the lowest Noack of all the base oil groups and they have better resistance to oxidation that PAO. However they are incredibly expensive and I'd see if you could live with PAO before considering the jump to esters.


I appreciate all the insight, I will probably go with the amsoil 10w30, probably the signature series, seems like it should work for my application with regular changes.

 

[bigj_16]

That sounds like a good way to go.

 

[BrocLuno]

OK, a few things to consider.

1.) Bigger turbo means higher incipient cylinder pressures. And along with the revised programing to keep the fuel in the right ratio when injected, will likely lead to fuel dilution issues with the oil.

2.) Who ever said Redline was not one of the best oils out there needs an education in severe service oils ... It is bought in 55 gallon drums at HUGE prices for teams running blown alcohol and fuel (nitro) cars because it can stand ridiculous heat, fuel dilution, and still make some semblance of lubrication. There are weekend turbo'd track day car owners here who are getting very good engine life and reasonable OCI's on Redline. Go look at the UOA's ...

3.) Higher Turbo pressures will lead to higher rod loading. That means the bearings will be under more pressure on the compression stroke and way more pressure on the power stroke. For that you need film strength and increased cushioning. 40 grade will be your minimum. 50 grade will be indicated for hot weather. So that means 2 changes a year, probably ...

4.) No guessing on when it needs to be changed. Pull samples at 2,500 and 3,500 miles and send them in for a UOA. If the lab says they are breaking down or are contaminated, figure out why they are, and adjust accordingly.

5.) True PAO and Ester based synthetics are all about in the same price range for the same HTHS. Amsoil, Redline, Motul, Castrol RS, Mobil racing oil - all likely around $12/qt/liter.

6.) with the increased pressures, you will have blow-by. Add a catch can on the PCV system and see what turns up. Use magnetic drain plug and keep an eye on it. Use oversized filter because you will be pushing thicker cold oil through it and you don't want it going into by-pass (more media good).

Get a crankcase temp gauge and keep an eye on oil temps ...

You built the engine that needs this stuff, you pay the price - or this is a short lived joke ...

 

[Haxir]

Originally Posted By: BrocLuno
OK, a few things to consider.

1.) Bigger turbo means higher incipient cylinder pressures. And along with the revised programing to keep the fuel in the right ratio when injected, will likely lead to fuel dilution issues with the oil.

2.) Who ever said Redline was not one of the best oils out there needs an education in severe service oils ... It is bought in 55 gallon drums at HUGE prices for teams running blown alcohol and fuel (nitro) cars because it can stand ridiculous heat, fuel dilution, and still make some semblance of lubrication. There are weekend turbo'd track day car owners here who are getting very good engine life and reasonable OCI's on Redline. Go look at the UOA's ...

3.) Higher Turbo pressures will lead to higher rod loading. That means the bearings will be under more pressure on the compression stroke and way more pressure on the power stroke. For that you need film strength and increased cushioning. 40 grade will be your minimum. 50 grade will be indicated for hot weather. So that means 2 changes a year, probably ...

4.) No guessing on when it needs to be changed. Pull samples at 2,500 and 3,500 miles and send them in for a UOA. If the lab says they are breaking down or are contaminated, figure out why they are, and adjust accordingly.

5.) True PAO and Ester based synthetics are all about in the same price range for the same HTHS. Amsoil, Redline, Motul, Castrol RS, Mobil racing oil - all likely around $12/qt/liter.

6.) with the increased pressures, you will have blow-by. Add a catch can on the PCV system and see what turns up. Use magnetic drain plug and keep an eye on it. Use oversized filter because you will be pushing thicker cold oil through it and you don't want it going into by-pass (more media good).

Get a crankcase temp gauge and keep an eye on oil temps ...

You built the engine that needs this stuff, you pay the price - or this is a short lived joke ...


I'm already past the 2,500 and 3,500 mile mark. Although I am still on a stock turbo on spring pressure (about 9lbs of boost max) and the car is pretty babied to be honest. I actually have a dual catch can setup. My pcv plate is located on the intake side of the block about half way between the head and oil pan. Stock has just 1 port for the pcv vale, i have an aftermarket plate with 3 ports, one is the pcv valve to a sealed catch can back to the intake mani, another port meet's and V's from the valve cover into a vented catch can back to the intake, and the 3rd port just has a small L shaped small breather right there just off the plate. Also have a vented oil air cap. So I think I should be pretty [censored] good for excess crankcase pressure come time when I have a new turbo and pushing a lot of boost.

I do need to get a magnetic drain plug to keep an eye on things. I use Wix filters, the ones made for synthetic oil. Called like XS or something.