Do modern oils clean Piston Rings?

[Trav]

I honestly cant say, it would take a lot more tearing into than I need/want to do with this engine in the future. I agree there probably are limitations for already coked and stuck rings. In an engine in relatively decent shape IMO it will clean minor deposits out and prevent more from forming but you cant fix broke.

 

[PimTac]

This is where we need a way forward machine that can show us 5-10 years into the future and give us the answers. It will be interesting to see engines that have ran on today's oils for say a 100,000 miles and compare thecrings and lands to what we have seen in the past.

 

[Bryanccfshr]

Wire brush In a solvent, parts cleaner (and a split barrel with kerosene as a kid) is the only way I have removed baked on carbon deposits from pistons. Of course running oils that resist deposits is the best bet, since most personally owned automotive engines will never be torn down before the vehicle is out of service, keeping the engines functional is the best bet. Most people will never see the rings and pistons from a car they own. A difference in shades of deposits without any improvement in performance...is irrelevant to most owners. Those owners are not dropping pans or borescoping their engines to compare cleanliness on the internet. I am sure doctors wished we were as enthusiastic about our colons!

 

[Bjornviken]

Originally Posted by tig1

I have used M1 oils for the last 40 years and have never experienced ring coking caused by carbon build up around the rings.

👍

 

[capsicum]

It depends on the contaminant, different fuels have different byproducts which require different oil formulations to deal with. eg Oil intended for high sulfur diesel will coke up the whole engine and turbo if you suddenly switch to a low sulfur fuel. And the coke in this case isn't actually carbon it is mostly hard calcium that was intended to neutralize sulfur compounds but now has nothing better to do, it is black due to a light coat of carbon. Now Crosshead diesels side step all this by sealing the crankcase from all blow by so the oil formula can focus 100% on lubrication and it lasts for thousands of hours, and the pistons are lubed with consumable cylinder oil freshly squirted a few drops on each piston stroke, thus with a change in fuel you flip a valve to a different tank of cylinder oil and the oil is always fresh and clean.

 

[SonofJoe]

It usually works like this... Piston deposits can arise from three distinct sources. 1) Decomposition of the VII polymer. The more polymer you have in your oil, the more deposits you tend to get. Synthetic oils tend to contain less VII polymer but you need to be careful how you interpret this. A synthetic 10W30 will contain less VII than a mineral 10W30 but a wide cross-grade synthetic 0W40 may well contain more VII than a narrow cross-grade mineral 10W30. 2) Oxidation of the oil. Unless you're still using an oil based on Group I stocks, you generally don't need to worry about this unless you're into extended OCIs. If you are into extended OCIs, synthetics oxidise less than minerals and will generate less deposits 3) Burnt oil. This could be due to worn valve seals or worn rings. However nowadays, the most likely source of burnt oil is light base stock, stripped out of the crankcase by hot blow-by & recycled through the PCV system. If you want to minimise burnt oil related deposits, use a low Noack oil. Synthetics tend to have lower Noacks than minerals but again you need to be aware of the wide cross-grade vs narrow cross-grade thing. Other things to bear in mind are that in terms of additives, polymeric ashless dispersants counter piston deposits, overbased metallic detergents do not. Heavy oils (or light oils that contain a reasonable amount of very heavy base stock) are way better at preventing piston deposits than light oils. Hope that helps...

 

[OilUzer]

Originally Posted by SonofJoe

... 3) Burnt oil. This could be due to worn valve seals or worn rings. However nowadays, the most likely source of burnt oil is light base stock, stripped out of the crankcase by hot blow-by & recycled through the PCV system. If you want to minimise burnt oil related deposits, use a low Noack oil. ...

Hope I'm not derailing the thread ... I've read suggestions/opinions that the recycled oil through the pcv is oil mist and independent of noack number. Question: is oil mist or vapour like water evaporating without being boiled? You would think the higher the noack number, the higher the evaporation in general regardless of "evaporation temperature". Mist is also liquid phase of vapor so again it can't be independent of noack number! No? Can you explain this please? Thanks.

 

[SonofJoe]

Originally Posted by OilUzer

Originally Posted by SonofJoe

... 3) Burnt oil. This could be due to worn valve seals or worn rings. However nowadays, the most likely source of burnt oil is light base stock, stripped out of the crankcase by hot blow-by & recycled through the PCV system. If you want to minimise burnt oil related deposits, use a low Noack oil. ...

Hope I'm not derailing the thread ... I've read suggestions/opinions that the recycled oil through the pcv is oil mist and independent of noack number. Question: is oil mist or vapour like water evaporating without being boiled? You would think the higher the noack number, the higher the evaporation in general regardless of "evaporation temperature". Mist is also liquid phase of vapor so again it can't be independent of noack number! No? Can you explain this please? Thanks.

I'll try and give you the honest answer... In the world of engine oil volatility/oil loss, there are three ways of looking at things. - There's real-life where a oil might spend say 250 hours fluctuating between ambient & 100°C - There's the Noack test which whacks up the oil to an unrealistically high 250°C for just one hour - Finally there are the industry standard engines like the Sequence IIIG which keeps the oil at 150°C for 100 hours on a cyclically operated engine. I can say absolutely categorically that with the industry standard tests (not just the US Sequence IIIG but also the European Peugeot TU5), oil consumption IS very Noack dependant. The correlation isn't perfect but nor would I expect it to be. In both tests, you can see from the used oil analyses, carried out during the test, that the oil is, for want of a better word, 'distilling', with simple, additive-free light base oil exiting the crankcase with the blow-by & leaving all of the heavy stuff in the oil in the sump. This implies true 'evaporation' of oil into the vapour phase; not just physically 'misted' fully formulated oil (although it's quite possible the two look alike to the naked eye). Just to highlight how big a deal this is, on the TU5, the oil contaminated blow-by is not returned to the intake system but cooled, condensed & vented. Put a 15% Noack oil on the TU5 and in 72 hours you might completely empty the sump of oil! However you usually get very clean pistons at end-of-test because no oil has been burnt. On the IIIG, oil contaminated blow-by is (just like on a real car) routed through the PCV/intake system and subsequently burnt. It's impossible to empty the IIIG sump of oil with a 15% Noack oil but I guarantee that the pistons will look diabolical at the end of the test! The big question, one that people like me can't honestly answer, is how does this all relate to real life, where the oil is generally cooler but exposed to hot blow-by for far longer? Instinctively I'd say this is less severe but some oil will ALWAYS get evaporated & burnt because that's how multi-component vapour-liquid equilibrium works. Also real life involves stuff like fuel dilution (something neither the Noack nor industry tests addresses) and the cyclic re-evaporation of condensed gasoline & water from the sump will act to exacerbate the distillation of base oil from the sump. So IMO, if you want clean pistons, think low Noack.

 

[Direct_Rejection]

Thank you Son of Joe. Tremendous stuff. My engine is a decade+ old design. Fuel Injection with Variable Valve Timing. There are reports of engine tear downs showing lots of carbon at the piston rings. Oil consumption appears to be an issue. Given my particular circumstances, I will be changing out my PUP 5W20 soon. Amsoil Signature Series 5W20 OR Mobil1 ESP 5W30 OR PP Euro L 5W30. LOL. I am becoming a Thickie.

 

[RDY4WAR]

Joe Gibbs Driven LS30 5w-30 is also a good consideration. The NOACK on it is around 6%.

 

[bunnspecial]

Originally Posted by Bryanccfshr

Wire brush In a solvent, parts cleaner (and a split barrel with kerosene as a kid) is the only way I have removed baked on carbon deposits from pistons.

I have found a used/broken piston ring to be one of he best tools around for getting carbon off of piston crowns and out of ring lands. That can be some stubborn stuff. The last time I had the head off the MG(which was a few months ago) I used a wire brush on a drill to clean up as much as I could. The head didn't have very many miles on it, and I had no trouble getting the combustion chambers and valve faces as clean as I felt like making them. They weren't spotless, but if I'd used a smaller brush to get into the crevices I probably could have made it there-I just didn't think it was that important. The block deck cleaned up fine with a wire brush(not as nicely as the head that had been machined 5,000 miles prior, but nice enough for a 100,000 mile, nearly 50 year old block that I doubt has ever seen a machine shop), but the pistons were another story. I could see carbon flying off of them when I hit them with he brush, but it didn't seem to make a difference. I was waiting on some parts to come, so spent a fair bit of time doing things like applying solvents(mostly kerosene and MMO), all of which would seemingly loosen it up but I still didn't make any real break-throughs until I stared using a ring as a scraper. That had them mostly down to bare metal with a few minutes of work on each piston crown. I'm SLOWLY rebuilding a short block that I plan to install, and got one piston cleaned up fairly well by soaking in kerosene overnight and then scraping with an old ring. I didn't try any of the others because I was uncomfortable with how out-of-square the lands were. A new set of pistons is ~$200, and all said and done I'll have $2500-3K in parts and machining in the rebuilt engine. I figured it was a false economy to try and save $200 by reusing what-to me-are questionable pistons. It would seem a waste to start up the rebuilt engine and have the rings never seat or not seat correctly because they're flexing too much in the lands.