Rotella and Soot

[MacheteJames]

Here's the deal. I had endless soot on the hatch until I began running Rotella T6 at 32,000 miles. I had been switching between Castrol Syntec 5w30 and Mobil 1 5w30 up to that point. With Rotella, no soot. At my last oil change (38k), I switched back to Castrol due to a thread I read in the Gen1 forum in which someone mentioned that Rotella may be a cause of intake valve deposits.

So, now that I'm back on Castrol, the soot is back with a vengeance. My question is - what is the mechanism by which Rotella helps with the soot issue? No other variables have changed here, so it's gotta be the oil. Is it something to do with the particular additive package in Rotella, vs other synthetics? Is Rotella potentially suspending the soot in the oil, which then somehow ends up on the backs of intake valves through the PCV system?

[speed23]

Are you talking about soot at the exhaust pipe? Oil will have no bearing on that.

[MacheteJames]

Originally Posted by speed23 Are you talking about soot at the exhaust pipe? Oil will have no bearing on that.

Yes. The soot that comes out of the exhaust and inevitably ends up on the hatch.

As for it having no bearing on the issue... why wouldn't it? I'm not a powertrain engineer, but if a particular oil is designed with an additive package intended to control soot, why wouldn't it have an impact? The marketing language for Rotella even states that shear stability and soot control are two of the strengths of the oil.

Shell Rotella® Products - Shell Rotella

@mituc;

[Tokay444]

Unless you're burning copious amounts of oil, it shouldn't be coming out of your tail pipe.
The soot is burnt fuel.
That's why.

[MacheteJames]

If you guys are right, then I don't have any explanation for the change in soot accumulation. Only other thing could be the temperature change between summer and fall. Also installed a TIP, but I can't see a just a TIP having such an effect. If I'm wrong, I'm certainly open to correction...

BTW, this was the original thread on oils:

Let's talk about engine oils

[mxlplx71]

If you have a smoking turbo sometimes changing to a thicker oil can solve it

[mituc]

If you can post a log while your tail pipe is smoking. If it is smoking that bad you should see that even in the AFRs. If the oil burns into the engine then the AFRs you see should be richer just because there's more unburnt gas and less oxygen.
And if you smoke that bad to the point the soot coming from the exhaust sticks to the hatch then I think something else is wrong, not the oil.

I assume the T6 you're using is 5w40, have you tried a petrol engine oil of the same weight? If the smoke is visible on the tail pipe, then what color is it?
Have you tried pulling the plugs and eventually changing them with some fresh and correctly gapped ones? Because I think your problems is with the ignition system or some O2 sensor, not with the oil.

[Tokay444]

The soot they talk about controlling is in the crank case, from burnt diesel...

[warjunkies]

Take a log at idle, then Sea foam the engine and have a smoke show, pull the plugs and replace with fresh and correctly gapped, pull the MAF and clean, fresh oil change, and take a new log at idle.


Sent from tapatitties.

[seriouscheese]

I have noticed this as well. I ran PP for the first 5000 miles off the lot, and had lots of soot on my hatch and carbon on my tail pipes. For the last 8000 miles, I have been running Rotella, and have noticed much less of both.

Honestly, I attribute this to me being smoother with the throttle over time. When a throttle impulse is applied, it takes a fraction of the second for the transience to settle in the air meter, so the ECU may "prime" the cylinder a bit to prevent a lean condition and ensuing ZZB. Just being smoother with throttle application should prevent this.

However, considering your anecdote makes me wonder if there isn't something more at play here. Maybe the Rotella handles fuel dilution better. Maybe other oils leave fuel deposits in the turbo housing which burn/flake off later. Maybe the thicker oil just generally prevents fuel blow-by to some extent. Who knows, but I have noticed similar results after switching to Rotella, though I lean towards that being a coincidence for the most part.

[Yatta]

Strangely I think I have noticed the same thing (less soot) on my CWP but chalked it up to seasonal.. (I run T6 Summer, PP Winter); UOA I have seen on MSF have shown more fuel dilution with PP; that means it is worse at controlling it, or more is getting by the rings; if more fuel is present in PP wouldn’t that mean that more is getting passed back through the intake via PCV ? We know the extra 10w on top masks turbo seals leaking but could it also be sealing compression slightly better then PP ? If that is true (lots of ifs I know) there would be more fuel in the crankcase, more in the PCV venting and we know that gets (in theory) pulled back into the intake; I certainly know my oil smells to hell of gasoline using PP and doesn’t smell so bad with T6.

[MacheteJames]

OK, so that's three of us, then.

I'll switch back to Rotella for the next change and see if the soot goes away. If it does, then there has to be something to this. Car is in perfect running order, BTW. Fuel trims are good, MAF was cleaned 1,000 miles ago, and no smoking turbo issue.

[tegxsi]

Interesting...I will have to give Rotella T6 a try.
The only thing that has cut down on soot on my rear hatch so far is stage1 OTS map. I still get it but it takes longer to build up. The tips of my tail pipes aren't 100% black anymore.

[mituc]

The tips of the exhaust are black since the car had 5 miles and had a totally fresh and clean engine from the factory, It's just a result of DI and how the mixture burns when the engine is cold. And if you get black smoke now I'd rather check the battery, ignition coils, spark plugs, boost leaks. Rotella or something else, if the oil was the culprit for smoke it would be blue smoke not black.

So if your engine spits too much soot then it's something else, not the oil. Rotella is not even by far a suitable oil for these engines. The fact that it can be used it's one thing, and being adequate is a totally different thing.
However, it may be just better than the cooking oils some people used prior to Rotella. Just switch to a decent synthetic oil.

Also, I'm not sure about others, but if my engine wasn't a diesel and had a problem with not burning the mixture completely I'd rather want that soot to come out of the tail pipe rather than being trapped by the tiny oil film in the cylinders where from with reduced flow properties and high contamination it has a very big chance to make its way back to the cylinders as vapors/soot via PCV/EGR and clog everything with black gunk.

[MacheteJames]

Originally Posted by mituc So if your engine spits too much soot then it's something else, not the oil. Rotella is not even by far a suitable oil for these engines. The fact that it can be used it's one thing, and being adequate is a totally different thing.

You just contradicted what has been long-time MSF wisdom - Rotella has been a go-to oil for this platform (as well as Subaru, Cobalt SS, SRT, and you name it) for a few years now. What evidence do you have that this oil is bad for the car, when so many others have used it with success?

[Cheapspeed]

I love soot out my tail pipe and all over my bumper. Like a subtle message of "I will WOT all over your face!"

[mituc]

Originally Posted by MacheteJames You just contradicted what has been long-time MSF wisdom - Rotella has been a go-to oil for this platform (as well as Subaru, Cobalt SS, SRT, and you name it) for a few years now. What evidence do you have that this oil is bad for the car, when so many others have used it with success?

Diesel truck engine oil - check;
Low SAPS (for diesel catalytic converters and particle filters) - check;

The UOAs people were doing showed that the oil is good. Unfortunately the UOAs do not show what's left in the DI engine, they show only what the oil carries out of the engine with it While the PI engines may be ok to some extent and under some driving conditions, the DI engines may not.
I'm not saying this oil is bad for the car, I'm just saying is not suitable. However, it may be better than the oils you used before, and that may be very well true. But that's different.

As far as I understand though the idea of this thread is not to compare oils, but to figure out why your car spits soot from the tail pipe (smoke + condensation + oil vapors + unburnt gas). Did you check those plugs yet? What mods do you have?

[Yatta]

Originally Posted by mituc Diesel truck engine oil - check; Low SAPS (for diesel catalytic converters and particle filters) - check; As far as I understand though the idea of this thread is not to compare oils, but to figure out why your car spits soot from the tail pipe (smoke + condensation + oil vapors + unburnt gas). Did you check those plugs yet? What mods do you have?

@mituc; , I have been using T6 (specifically) in Audis, VWs and now my MS3 for over 10 years, when I started using it, it was not API-SM rated (it is now), a couple of years back it was reformulated to reduce zinc content specifically for use in gas engines, so not suitable? Maybe at one point it was not well suited as it could harm gas catalytic converters but only if you burnt oil. The only thing I have heard that concerns me about T6 is that is seems to not do so well for the folks running on E85, might be causing issues with the CDFP and ‘black’ death gunk, being ok for diesel and gas is one thing but ethanol might be asking too much.


The question on this thread isn’t why we make soot, its the best prius repellent you can find and it is a symptom of the stock tune (and some others) being pig rich, the question is why it seems to soot less when we run T6.

[seriouscheese]

Shooting soot out the back of a GDI engine with a fairly large turbo on it is not unusual at all though. My brother's GTi does the same thing, and I've heard similar things about the Hyundai GDI turbos as well.

Why this happens isn't really the question. Without a doubt, it partially (primarily) comes from cylinder priming and other sources of unburnt gas/oil during normal operation. The question here is "does Rotella reduce soot somehow, and if so, why does it reduce the soot, and how can we confirm this in a controlled manner?"

To the first question, it seems plausible at least. A number of people have made the same observation here. Obviously this is a small sample of anecdotes, but it should at least indicate that the question is worth exploring further.

To the second question, some plausible explanations have been offered. We know that the Rotella, for whatever reason, prevents or handles fuel dilution better than other oils (this has been confirmed by countless people, and is one of the primary reasons offered for why T6 is good for GDI engines). We know that fuel blow by creates positive crank case pressure, and we know that the more volatile gasoline vapors tend to vent more readily than less volatile oil vapors. This raises the possibility that unmetered fuel vapor could be reaching any part of the engine connected to the intake, including the turbo compressor, intercooler and valves. If T6 is preventing blow-by (perhaps just because it is thicker) or if it has detergents which somehow break down or sequester gasoline, then it makes perfect sense that reducing this source of unmetered fuel could reduce soot production.

For the last question - there are a number of controlled tests which could be performed. Simply observing the soot and carbon buildup on the hatch and tailpipes using different oils would be a start. It might also be useful to try another 5w-40 oil to see if it behaves the same (which would suggest that the the thicker oil actually creates a better compression seal). It might also be worth inspecting some EGR valves on people who have run Rotella versus other oils long term, to see if carbon fouling inside of the EGR system is correlated with oil type and soot production. I'd also be generally interested to see if EGR fouling and intake valve fouling are correlated at all (they almost certainly are, but it's worth checking out).

I also wonder if altitude might play a role in baseline soot production, since it should theoretically create a rich condition the higher up you go. This could explain why some people never see much soot at all. My car is driven daily at around 2200ft above sea level. Maybe I will switch over to PP the next time I visit my family on the coast to see if it produces soot the same way it does in the mountains.

For what it is worth, my MS3 is bone stock (except for a K&N oiled air filter and AP w/OTS stage 1), has 14000 miles on it, and made soot the day I drove it off the lot until the day I started using Rotella, which was on my third break-in oil change at 5000 miles. Once again, for what it is worth, I have been using the FRAM "Tough/Extra" guard oil filters with the full metal construction and synthetic/glass/whatever media.

[mituc]

Originally Posted by Yatta @mituc; , I have been using T6 (specifically) in Audis, VWs and now my MS3 for over 10 years, when I started using it, it was not API-SM rated (it is now), a couple of years back it was reformulated to reduce zinc content specifically for use in gas engines, so not suitable? Maybe at one point it was not well suited as it could harm gas catalytic converters but only if you burnt oil. The only thing I have heard that concerns me about T6 is that is seems to not do so well for the folks running on E85, might be causing issues with the CDFP and ‘black’ death gunk, being ok for diesel and gas is one thing but ethanol might be asking too much. .

I know people who used transmission oil in their engines and were fine. That doesn't mean that they should have done that. Same for diesel truck oil.

Now, about the black death of the DI pumps, let's just say that the E mix people see it in less than 2k miles, a smaller concentration of ethanol which is very usual (6-10%) in the regular and even more premium gas will lead to the same thing but a lot slower.

As we all know the petrol DI engines tend to produce quite a lot of soot. A low SAPS oil means at least two things:
1. medium to mediocre lubrication properties (yes, the oil base plays a significant role in lubrication, but so does the phosphorus and sulfur ash);
2. poor additives package which 100% and always means that the oil doesn't have too many ash arrestor additives (I'm talking about that ash produced by the engine, or soot, the same soot you find later in your pump or on your valves).

The fact that the oil is somehow sticky and the base very eager to retain the ash even from the cylinder is not something I'm really thrilled about considering that I'll find a significant amount of it clogged on the valves and more.

So if you determined that by using rotella you smoke less then just use rotella, I can't stop you from following the "wisdom" of a small group of people on this forum and on some others I don't care about. Just beware that your engine isn't as clean as the OUAs show you and if you will pull the intake manifold and find your valves completely clogged with stuff don't even post on the forum, clean them and stay quiet.

[Yatta]

So, in your opinion Low SAPS oil is a poor choice for our vehicles? Rotella T6 will never carry an ILSAC rating, but is API-SM and Mazda has used 5w-40 to control smoky turbos in the past (on DISI engines)

From the User Manual:

The quality designation SM, or ILSAC
must be on the label.


as to low SAPs, truly low saps is sub 1.0% and T6 is right at 1.0% sulfated ash; Ford and Mazda both have both embraced low saps to their initial fill for both petrol and diesel, as this was initially a thread on soot, tell me, which oil is better suited to our motors? As I understand it, low SAPS is the result of a test where sulphuric acid is used to burn oil and what is left is what is measured; I suspect you will find the people using T6 for DI/Petrol is slightly more than a handful and not just on MSF.

[pzr2874]

This is what I've always followed:

Low SAPS oils: ACEA warning | Passenger Car Motor Oil (PCMO) - Gasoline Cars/Pickups/Vans/SUVs | Bob Is The Oil Guy

&

Does high TBN mean high/best quality oil? | Passenger Car Motor Oil (PCMO) - Gasoline Cars/Pickups/Vans/SUVs | Bob Is The Oil Guy

Take it with a grain

[crankshaft]

FWIW, I solved the soot (or snot) problem simply by changing my driving habits....which also may mean that change in the weather can be a factor. When I start it cold, I BABY it not just until warm, but until a time that I believe the exhaust system is warm and no longer dripping condensation. My theory was that the "boogers" were a result of the soot coming out clumped and wet.

[tmulls3622]

Guys just to throw my thoughts out there. I've been using Pennzoil platinum 5-40 Euro for the past probably 10k miles. The 40 weight holds up better then a 30 with the high heat and fuel dilution from the DI. I have also debated using T6 since it's made for diesels which are DI anyway but have heard otherwise that diesel oil will leave ashy deposits internally and can also mess with emissions and cats, but I'm sure most of us don't have those anymore I have also read on the forum that after people have had multiple oils tested after 3k miles that PP holds the best composition, topping Castrol, Mobil, even Royal Purple