Carbon buildup on Toyota pistons and rings

Originally Posted By: ARB1977

Here’s the top of one of my pistons on my 2015 Tacoma. No oil burning. Going to try Amsoil PI every 5K till 30K when it’s time to change plugs again and hopefully it cleans it up.


What does changing your plugs have to do with carbon build?
 
Originally Posted By: rollinpete
Originally Posted By: incognito_2u
So, As you can see, The 1999 Corolla that's in my sig is a car that's notorious for burning Oil......a product of not enough drain holes or too small a drain hole by the Piston oil control ring groove that eventually gets "clogged" and creates an "oil Burning" condition. Now the car in question was purchased 10 months ago, used, from a little old lady (literally) who had the car serviced by a reputable Service center in the area that has a great reputation of doing quality Work for a fair price.....upon looking at the service records of the vehicle (specifically the Oil Change records), the Oil used was Bulk dino Pennzoil 5W30 with a Pennzoil Oil filter, approximately every 5000miles/6 months. What I have done to possibly prevent this from being an issue was to give it an initial "Kreen" piston soak and to change the Oil to 5W30 Pennzoil Ultra Platinum with an Fram Ultra Filter.
I truly believe that the steps I took to cure/prevent the oil burning issue have worked!!
lol.gif

So far, 4 thousand miles on the car since purchase and it hasn't burned a drop of oil......


Whats your kreen piston soak? Thanks...



Remove spark plugs, add 3 ounces of “Kreen” through spark plug holes, rotate engine one full turn and repeat.
Let sit overnight, then turn over engine with spark plugs still removed. ( Clears out residual fluid)
Put plugs back in, start engine and let the smoke show begin.
Run car for 20 minutes, stop car, change oil / filter and your good to go.
 
The Prius also suffers from the same issue - I think the start/stop nature of it exacerbates the problem, the engine can be worked hard but shuts down completely when the car coasts. Maybe if Toyota designed the engine to "windmill" during deceleration with no fuel just to get the oil pump spinning to keep the rings free...
 
Originally Posted By: MONKEYMAN
Is it poor design or the oil?


Both! The Toyota (again) sees improper piston thermal management and oil circulation around the rings, like they have in prior engines series. IDK what their problem is- maybe try to gain FE by not cranking up combustion temps? Hasn't been working for them for DECADES, they need to take the hint.

The careless design alone, however, isn't an automatic death sentence. Short OCIs and/or less polymer-laden oils (like synthetics, but not exclusively synthetics) can mask the issue ie. NOT following the poor advice in the manual regarding minimum quality and OCI. When the engine's neediness for maintenance is met (using higher quality oil and/or shorter OCI than the literature suggests), they can survive without warranty work, like a normal engine.
 
Hmm, the old [censored] conventional bought the synthetic kool-aid argument again? What we don’t know is the service history of that vehicle including the oil choice. What we do know, as mentioned by the narrator of the video, is the effected vehicles are MY2007 and up. Well guess what, in 2007 the oil recommendation changed from 5W30 to 0/5W20 for the 2AZ-FE engine (look up the OM’s and you’ll see). So that begets the question: was it a poor engine design or a poor choice of oil viscosity to meet CAFE? By the look of those pistons it certainly looks like an oil sealing issue to me. To that point part of their warranty fix was to add higher tension rings.

It just so happens my previous two vehicles had the 2az-fe engines: 2004 Camry & 2010 Xb. Both received a diet of 5/10W-30 conventional oil of mainly Castrol GTX and later Mobil Super 1000. Both ran like a charm with no oil burning issues. Blow by was not a problem either with the oil colour staying within the light to dark amber range during the OCI.

As far as engine deposits and wear, that’s covered by the API/ILSAC certs. The sequence IIIG seems gruelling enough for me to have confidence my el cheapo dino is up to the task as my daily, non race track, driver.

Here’s a blurb written by one of our more esteemed members, TomNJ, you might find interesting:

Believe it or not, all else being equal Group I base oils are less prone to carboneous deposits in high temperature thin film environments than Groups II, III or IV. The higher aromatic content in Group I oils make them more polar and increase solvency, which can reduce deposits by dissolving polymeric oxidation by-products before going to carbon. See this thread from the past:

http://www.bobistheoilguy.com/forums/ubb...3300#Post803300

Not all VI Improvers contribute to deposits - some such as high shear stable dispersant types can be quite clean. I believe the GM ban of 10W-40s was based more on political and marketing concerns than ring sticking.
High temperature stability and coking tendencies are two very different properties. The broad term "high temperature stability" includes oxidative stability (resistance to reaction with oxygen), thermal stability (resistance to degradation by heat), hydrolytic stability (resistance to reaction with water) and coking propensity (tendency to lay down deposits). Most test methods involve various combinations of these conditions and therefore do not all give the same results. A base oil that has excellent thermal and oxidative stability such as PAO can give terrible coking, while a base oil with weaker thermal stability such as diesters can give excellent oxidation and coking results.

The coking test used in the reference link combines thermal stress (540F), oxidative stress (air flow over oil film), hydrolytic stress (water saturated air), volatility (thin film at high temperature), and solvency (oil flowing over residues). Solvency plays a major role in coking and often reverses the correlation of coking to other high temperature properties. A polar oil with good solvency will dissolve or disperse degradation by-products before they can polymerize into insoluble carboneous deposits.

PAOs and many Group IIIs are completely paraffinic and have virtually no polarity to dissolve degradation by-products. While they will breakdown more slowly than a Group I due to their superior thermal and oxidative stability, their solvency is so poor they just can't cope with polymeric degradation by-products and lay them down as deposits. Group I oils breakdown more quickly, but are better at cleaning up their own mess due to their higher polarity.

In a motor oil, all else being equal, higher groups would give longer life and less oil thickening than Group I. In theory they would not be as clean as Group I, but in reality the additives are adjusted to correct this deficiency. But no, they would not give less coking than Group I based oils unless dosed up with esters or high detergent levels.

Tom NJ
 
ndfergy, there's no way it's only the oil. How many other manufacturers regularly engage in consumption-related recalls across a variety of engine series and generations? Plenty of engines out there with the same oil, their rings remain free and of the originally-specified low-tension variety. What is Toyota missing?

Using 10W30 at least sometimes was probably very fortunate for you with your AZs
 
Originally Posted By: nthach
The Prius also suffers from the same issue - I think the start/stop nature of it exacerbates the problem, the engine can be worked hard but shuts down completely when the car coasts. Maybe if Toyota designed the engine to "windmill" during deceleration with no fuel just to get the oil pump spinning to keep the rings free...


I have a 2013 Chevy Volt. The previous owner mostly ran it on gas. The engine in the Volt runs at WOT the majority of the time that it's running, with excess power used to charge the battery, and when enough charge has been built up, it shut the engine off and runs off the battery, then runs the engine again when the charge is depleted. This cycle continues as long as the car is running on gas.

When I changed the sparkplugs at 94k miles, I saw no carbon on top of the pistons. It uses no oil.

I switched it to Mobil 1 5W30 and added Kreen to the oil. After it had used 25 gallons of gas, I cut the oil filter apart. I saw many tiny chunks of carbon in the filter. I replaced the filter with a new one and added more Kreen to the oil.

My main reason to add Kreen is because the part of the valvetrain I could see through the oil filler cap looked a little filthy. I also had some left-over Kreen so I figured I'd use it.

The chunks of carbon that the Kreen and/or Mobil1 are removing are, I think, less from the start-stop operation of the engine and more from questionable previous oil change maintenance by the previous owner. (The car was a repo and I got a very good deal on it).
 
Originally Posted By: nthach
The Prius also suffers from the same issue - ... Maybe if Toyota designed the engine to "windmill" during deceleration with no fuel just to get the oil pump spinning to keep the rings free...
Guess what!? Above about 45 mph, it does that, although not primarily for that reason.
 
Originally Posted By: CR94
Originally Posted By: nthach
The Prius also suffers from the same issue - ... Maybe if Toyota designed the engine to "windmill" during deceleration with no fuel just to get the oil pump spinning to keep the rings free...
Guess what!? Above about 45 mph, it does that, although not primarily for that reason.

I used Torque Pro and a Carista OBD-II dongle for laughs and giggles to monitor the OBD datastream and when I was coasting the engine was at 0 RPM. I occasionally throw the car into B nowadays just to kick the engine over while coasting.
 
Originally Posted By: nthach
Originally Posted By: CR94
Originally Posted By: nthach
The Prius also suffers from the same issue - ... Maybe if Toyota designed the engine to "windmill" during deceleration with no fuel just to get the oil pump spinning to keep the rings free...
Guess what!? Above about 45 mph, it does that, although not primarily for that reason.

I used Torque Pro and a Carista OBD-II dongle for laughs and giggles to monitor the OBD datastream and when I was coasting the engine was at 0 RPM. I occasionally throw the car into B nowadays just to kick the engine over while coasting.
Interesting. Evidently those aren't giving good data when the injectors (and ignition, too, I assume) are shut off with the engine rotating. The programming forces the engine to rotate when the car is above certain speeds in order to avoid over-speeding motor-generator "MG1", the one connected to the sun gear of the planetary gearing. You can feel a slight jolt (which feels a bit like a conventional automatic transmission shifting) when the engine stops or starts rotating due to car speed rising above or falling below the threshold speed while coasting.
I use a ScanGauge, which, when set in "hybrid" mode, does show the motored engine speed, which normally settles around 992 to 1000 RPM (when it isn't zero) while coasting at moderate speeds. Above a certain fairly high road speed, it must go faster to protect MG1.

So far, my Prius consumes remarkably little oil. I'm paying attention to any credible clues here as to how to keep it that way. Opinions vary widely on ways to minimize the problem in susceptible engines---apparently including (some?) Prii, as you said. I've seen claims that it results from oil viscosity too high, oil viscosity too low, short trips, sustained high speed driving, conventional oil, synthetic oil, oil volatility, the EGR system, lack of a PCV catch can, low quality fuel, VII's, and more.
 
This problem is not specifically due to VII polymer. Nor is it due to oils based on 'conventional' Group II base oils per se. It also has very little to do with whether you run with a short or long OCI.

What's happening in these engines is happening as a result of running oils with too high a Noack volatility. More specifically, it is the combination of running a high Noack oil in an engine with too much blow-by or blow-by that is too hot or where the PCV system it permitting too much blow-by.

The hot blow-by gas is 'stripping out' the light front-end of the lightest base oil in the engine oil. This is traversing the PCV/Intake system and being burnt in the combustion chambers. Base oil does not burn cleanly and leaves behind gummy deposits. Most of these will leave with the exhaust gas, some will settle on the piston crown and some will find their way passed the rings. The top two rings are self-cleaning but the oil control ring isn't, and that's where the gummy deposits accumulate. It doesn't help that the oil rings run relatively cold so there's a condensation/increasing viscocity thing going on with the deposits.

This process happens at a glacially slow pace but a point is reached (usually around the 50 - 60k mark), where either the drain holes gum shut or the OCR 'glues itself' flush with the groove (at which point oil consumption rockets!).

You can do several things to prevent this problem. You can run a synthetic oil because all things being equal, synthetics have a lower Noack that conventionals. You can run an oil with a higher W-rating (ie run a 10W30 instead of a 5W30 and preferably run a 15W40) because W-rating has far more influence of an oil's Noack than its weight. You can run a narrower cross-grade oil (ie run a 10W30 as opposed to a 0W40). You could use a non-ILSAC oil (API only oils should in theory gave a lower Noack) or use an ACEC/dexos oil. Or alternatively you can buy a different car which is less sensitive to Noack related issues (tighter/thicker rings, runs colder, has better PCV design).

The problem with this problem is once you have gummed stuff up, simply switching to a better oil, won't help as once out of solution, deposits rarely want to go back in. This is a problem that needs to be prevented, not cured.
 
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I do agree high quality oils can handily mitigate ring coke and varnsih issues, and am 100% on board for advocating the most stable oils with low volatility, but have a tough time believing the toyotas just get the worst oil out of all the engines on the road. The AZ certainly isn't offering ANYTHING over other engines- at best we're talking middling fuel economy, middling output, middling emissions, middling NVH ... it's such a terribly average engine that offers nothing (zip, zilch, nada) over same-class engines like a Honda K, MZR/Duratec or even an Opel/GM Ecotec that would require specialty, top shelf oil. This class of engine are installed in cars that routinely get the cheapest bulk conventional oil and neglected OCIs. What about the Toyota makes it the most prone to failure by this mode, to the tune of several recall campaigns?
 
Originally Posted By: PeterPolyol
What about the Toyota makes it the most prone to failure by this mode, to the tune of several recall campaigns?


Simple, it's a Toyota. Toyota can get away and routinely gets away with all sorts of shortcomings and people will still praise it. This thread is a prime example of that because the oil was one of the first things mentioned.
 
I suspect that even the mighty Toyota didn't understand or anticipate the problems that this engine was having, as so much of this depends of the confluence of different factors.

I suspect like most OEMs, they were under pressure to improve fuel economy. You can improve FE by moving to higher compression ratios and to thinner, low tension rings. The price you pay for this is higher rates of hotter blow-by.

The Toyota issues go way back and to a certain extent, they probably coincided with the shift in the US from 10W30 to 5W30. The US, mistakenly IMO, made 5W30s from first generation all Group II base oils which took the volatility of oils right upto the 15% limit.

Put the two things together and you've got ideal conditions for forming 'over-the-top' gummy deposits. I dare say that these engines were also more prone to dropping gasoline into engine oil. The repeated gasoline condensation/evaporation cycle will exacerbate the amount to light base oil that gets evaporated into blow-by & burnt, further worsening the problem.

Although they probably didn't realise what impact it would have, I'd personally accuse the API & ILSAC of contributing to this field problem by allowing oils to qualify for GF-4 with appallingly bad Sequence IIIG Weighted Piston Deposits.

I always wondered why Toyota were so quick to accept responsibility for this issue when it looks to me like other parties were equally at fault.
 
Originally Posted By: CR94
Interesting. Evidently those aren't giving good data when the injectors (and ignition, too, I assume) are shut off with the engine rotating. The programming forces the engine to rotate when the car is above certain speeds in order to avoid over-speeding motor-generator "MG1", the one connected to the sun gear of the planetary gearing. You can feel a slight jolt (which feels a bit like a conventional automatic transmission shifting) when the engine stops or starts rotating due to car speed rising above or falling below the threshold speed while coasting.
I use a ScanGauge, which, when set in "hybrid" mode, does show the motored engine speed, which normally settles around 992 to 1000 RPM (when it isn't zero) while coasting at moderate speeds. Above a certain fairly high road speed, it must go faster to protect MG1.

So far, my Prius consumes remarkably little oil. I'm paying attention to any credible clues here as to how to keep it that way. Opinions vary widely on ways to minimize the problem in susceptible engines---apparently including (some?) Prii, as you said. I've seen claims that it results from oil viscosity too high, oil viscosity too low, short trips, sustained high speed driving, conventional oil, synthetic oil, oil volatility, the EGR system, lack of a PCV catch can, low quality fuel, VII's, and more.

I'm betting the ScanGauge can access more PIDs than a ELM327 dongle and an app can. As long as the cams and crank turn, both CMP and CKP sensors(G and Ne sensors/signals on older Toyotas) would still throw out AC voltage. I'm guessing the tach signal is based off injector or coil pulses.

This car was on PP and M1 for most of its life - in the 5W-30 flavor. I was able to get the oil consumption down with the use MMO about 500 miles out from an OCI. I did a engine flush with Lubro Moly's Engine Flush 2 years ago. I now have Schaeffer's Neutra 131 circulating in the oil with a top off of the cheapest 5W-30 I can find(ST).

My suspicion is ring coking - which is a common issue on the Corolla and Camry of the early-2000s. Toyota has been seeing the 3rd gen Prius with oil consumption issues as well. Blame 5W-30 all you want - but the Lexus V8s are speced for either and I've ran 5W-30 in a 1991 LS400 with the original version of the 1UZ-FE and it didn't use oil. The Sienna in my parent's garage also uses 5W-30 of various flavors(PP, M1, Castrol, Valvoline and Chevron) and it doesn't really use oil either.
 
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Good sunlight ...
... all vehicles and lubes are less than perfect hence the pursuit of the perfect OCI ...
 
Originally Posted By: SonofJoe


Although they probably didn't realise what impact it would have, I'd personally accuse the API & ILSAC of contributing to this field problem by allowing oils to qualify for GF-4 with appallingly bad Sequence IIIG Weighted Piston Deposits.


GM and Ford were both specifying 5W-30 before there was an ILSAC, let alone a GF-4 spec. This was in the days of API SF.
 
Originally Posted By: KrisZ

Simple, it's a Toyota. Toyota can get away and routinely gets away with all sorts of shortcomings and people will still praise it.


Yep, if it was a Mitsubishi, this thread would be twice as long, and all filled with hate for Mitsubishi...but it's a Toyota, under the carpet with all their other problems.
 
Originally Posted By: brianl703
Originally Posted By: SonofJoe


Although they probably didn't realise what impact it would have, I'd personally accuse the API & ILSAC of contributing to this field problem by allowing oils to qualify for GF-4 with appallingly bad Sequence IIIG Weighted Piston Deposits.


GM and Ford were both specifying 5W-30 before there was an ILSAC, let alone a GF-4 spec. This was in the days of API SF.




Having OEMs speccing oils for new cars and the shape of the actual overall market are two different things entirely. There is significant 'lag' in the system as older cars persist in the vehicle parc which keeps older viscocity grades alive.

This 2012 article by Infineum includes a chart showing how the engine oil market in North America was seen to be evolving by viscocity grade.

http://www.infineuminsight.com/insight/dec-2012/how-low-will-viscosity-go

Note how in 2000 (around about the time GF-3/SJ was being changed to GF-4/SL), 5W30 made up just 15% of overall sales with 10W30 being by far the predominant grade. It could well have been that the problematic Toyota engine design derived from a time when oils were thicker and less volatile. Hence my suspicion that they were inadvertantly caught out by changing circumstances which the did not foresee.
 
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