I like to keep abreast of latest industry news in lubrication and I came across one person representing an industry body involved in setting new lubricant specification’s for engines. This person was arguing that future lubricants should be totally no SAPS for engines.

Now the trend has admittedly towards lower and lower SAPS oils over the years. But no SAPS at all does seem a step potentially too far, in that what protection do lubricated components get in this deal?

Is ash really that bad and do SAPS deserve the “e-number” like reputation they have when the ash forming components are there for a good reason. So I suggest…wait, hang on a minute….I have actually started this article in the middle of the story rather than the start of SAPS story. For a new reader already confused this may feel similar to joining a new Netflix show on season 2 episode 6. The story you are sure should make sense but no back story makes it confusing. I have not even explained what are SAPS or ash or why they are good or bad. So let’s do a season recap for this article before we proceed.

Previously on Learn Oil Analysis…

What are SAPS or Low SAPS?

SAPS stands for sulphated ash, phosphorus and sulphur. So let’s break these down into what each means.

What is Sulphated Ash?

Sulphated ash is a measure of the amount of non-combustible metallic additives present in lubricating oils and fuels. That sounds a mouthful and we are only halfway through the first two letters of SAPS and have a load of new concepts to understand. So it’s non combustible; ie the stuff left behind after burning your oil/ fuel, but what do we mean by metallic as it’s not necessarily what you think. Well first, metallic is the chemistry sense of metallic which goes beyond what we think of in every day as metallic. So in chemistry terms metallic is groups 1 (excluding hydrogen) and 2 of the periodic table plus the transition elements. Groups 1 and 2 include elements like calcium and magnesium. Calcium we think of as substances like chalk (calcium carbonate) or as part of our teeth or bones, calcium is not often thought of as metal the same way you would think of iron or tin for instance. The ones you think of as metal are actually a subgroup called the transition element metals and are the more traditional metals you think of like iron, copper, lead, tin, zinc etc. So a big chunk of the elements we encounter count as metals, so it may be easier to say what doesn’t count. In this case things like carbon, oxygen, nitrogen and hydrogen are all non-ash forming which are usually what your base oils are made of.

So this means the base oil itself is non ash forming, but most the stuff oil companies put in the oil as additives are ash forming.

These additives, typically metallic detergents and anti-wear agents, are crucial for enhancing the performance of the lubricant, otherwise your engine would fail. When the oil is burned (find out why in the box below) during engine operation, these metallic additives leave behind residues. Sulphated ash is determined by burning a sample of the oil and then treating the residue with sulfuric acid to convert all the metal compounds into their sulphates. The resulting material is weighed to quantify the sulphated ash content.

Why does oil burn (surely it’s the fuel that burns)

Well normally you think of the oil in your sump and the fuel and air at the top of the engine. You have these things called piston rings that separate the two. So how is oil still burning? It can be a faulty piston ring when in excess, but even ordinarily fully functioning rings don’t separate the oil fully from the sump. Why? Well the rings don’t actually do the sealing. Confused? Yes that’s right they come close to the bore, but the oil actually forms the gap between the ring and the liner the final microscopic seal. You may say “yes but don’t the rings scrape that off when it goes down the bore”, which is true, but the bores are honed with tiny grooves in the liner to hold oil to assist lubrication and sealing. These are always present and topped up as the rings come back up, but also exposed to combustion temperatures and hence will burn. So over time a small amount of oil is normally burnt. For a typical family car this can be between 150ml and 700ml a year depending on engine type, sump size, driving style etc and this oil burning is what is of concern when we talk about SAPS. It is also worthwhile noting a poorly performing car that has serious piston ring wear for instance could consume double or triple these numbers. Hence it’s worth noting you can reduce SAPS too much to the point the reduced per ml ash formation is outweighed by the increased volume of oil burned from worn piston rings. As I will point out later, everything is a balance.

Laboratory Measurement of Sulphated Ash

In a laboratory setting, the process of measuring sulphated ash involves several key steps I have simplified below:

1. Sample Preparation: A precise amount of the oil sample is weighed and placed in a combustion crucible.
2. Combustion: The sample is burned in a controlled environment, usually in a furnace, until all combustible material is gone, leaving only the ash.
3. Sulphation: The residue is treated with sulfuric acid and heated to convert metal oxides to sulfates to allow standardised weighing.
4. Weighing: The remaining sulphated ash is weighed to determine the concentration of metallic additives in the oil.

This value is expressed as a percentage of the original sample weight.

What are the sulphated ash categories?

There are a few classification ranges based on industry and engine types but for example methane gas engine manufacturers specify the range of sulfated ash content suitable for each engine they market. These ranges vary, but generally are:

• Ashless = <0.1%
• Low ash = 0.1 to 0.5%
• Medium ash = >0.5 to 1%
• High ash = >1% and can be 2 or 3% in some circumstances although rare to have this high.

In car markets specifications like ACEA ratings may be used. For instance at time of writing the C rating has:

• Low SAPS = < 0.5%
• Mid SAPS = 0.5 to 0.8%
• High SAPS = >0.8%

However it’s always best to check for application and fuel types the groupings as small car engines with clean fuels will generally need less protection than large marine engines that have to burn much more aggressive fuels nobody else will accept for land based equipment.

Sulphated Ash in Engine Oils: A Delicate Balancing Act

Ash can be a Jekyll or Hyde so let’s meet both.

Dr Jekyll: Benefits of Sulphated Ash

• Guardian of Valve Seats: In engines, particularly those running on methane gas, valve seats are constantly under siege from high temperatures and pressures. Sulphated ash forms a protective layer, warding off the detrimental effects of metal-on-metal contact. This is crucial in gaseous engines, where the absence of liquid fuel means less inherent lubrication. The right amount of sulphated ash in oil can significantly reduce valve seat recession, prolonging the engine’s life. As we move from methane to hydrogen the temperatures only increase and the requirement for ash will only increase.
• Detergent Properties: Like a vigilant cleaner, sulphated ash in engine oil keeps internals free from harmful deposits and neutralizes acidic by-products from combustion. This is particularly vital in maintaining engine cleanliness and efficiency.
• Acid Neutralization: The Total Base Number (TBN) of engine oil is a measure of its ability to combat acidity. Sulphated ash contributes to this, ensuring the oil can effectively neutralize more acidic by-products, thus safeguarding engine components, including valves, from corrosion.

Mr Hyde: When Too Much is Too Bad

However, like too much salt in a dish, excess sulphated ash can spoil the engine’s performance.

• Ash Deposits: High sulphated ash content can lead to deposits in the combustion chamber. This is problematic, as these deposits can break off and disrupt the combustion process. Imagine fragments of ash acting as unwelcome guests in a precisely timed dance of engine combustion.
• Tunneling Effect: When chunks of these deposits break away, they can create pathways for combustion gases. This tunneling effect disrupts the engine’s compression and can lead to a loss of efficiency, increased emissions, and potential engine damage.
• Emission Concerns: In today’s environmentally conscious world, the impact of sulphated ash on emissions cannot be ignored. Excessive ash can hinder the performance of emission control systems, making it challenging to meet stringent environmental standards.
• Lubricant Performance: While metallic additives are essential for the protection and performance of engines, excessive sulphated ash can be detrimental. Balancing the additive concentration is critical to ensure optimal performance without compromising engine cleanliness and emission control.

So we hopefully have a basic understanding of sulphated ash now so let’s review the other two parts of SAPS – sulphur and phosphorus.

Sulphur / Sulfur and phosphorus

Call me a traditionalist but I still use the “ph” spelling although the American “f” sulfur terminology is now the official international spelling for the word sulphur. So for my American audience please bear with me as I will use the original British spelling for the rest of this article. Both sulphur and phosphorus are non metals, so why are they important in this SAPS discussion. Well SAPS isn’t all about the ash it’s about environmental impact. Both sulphur and phosphorus are excellent anti-wear additives, but they have their drawbacks.

Why Sulphur and Phosphorus Can Be Detrimental in SAPS

While sulphur and phosphorus are essential for the performance and protection of lubricants, their presence can also lead to several negative effects, especially concerning modern engine technologies and emission standards. Here’s why:

Impact on Emission Control Systems

1. Catalytic Converters: Phosphorus can poison the catalysts in catalytic converters, which are critical for reducing harmful emissions from the exhaust. This poisoning reduces the efficiency of the catalytic converter, leading to higher emissions of pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons.
2. Diesel Particulate Filters (DPFs): Sulphur in the oil can lead to the formation of sulphated ash during combustion by providing the sulphur to react with the metals mentioned earlier. This ash accumulates in DPFs, causing them to clog more quickly. Clogged DPFs require more frequent regeneration cycles to burn off the accumulated soot and ash, which can increase fuel consumption and reduce engine performance.

Engine and Oil System Contamination

1. Engine Deposits: High levels of sulphur and phosphorus can lead to the formation of engine deposits (not ash but just as problematic), such as sludge and varnish. These deposits can block oil passages, interfere with valve operation, and reduce the efficiency of heat transfer, potentially leading to overheating and increased engine wear.
2. Oil Contamination: As the engine oil degrades over time, the sulphur and phosphorus compounds can break down into corrosive acids. These acids can cause corrosion of engine components, further reducing engine life and efficiency.

Environmental Concerns

1. Air Pollution: Higher sulphur levels in fuel and lubricants can lead to increased emissions of sulphur dioxide (SO2), a significant contributor to air pollution and acid rain. Acid rain can have harmful effects on the environment, including soil degradation and water body acidification.
2. Regulatory Compliance: Environmental regulations are becoming increasingly stringent regarding the permissible levels of emissions from vehicles. High sulphur and phosphorus content in lubricants can make it difficult for vehicles to meet these standards, leading to potential legal and financial penalties for manufacturers and owners.

Balancing Benefits and Drawbacks

While sulphur and phosphorus are beneficial for their protective and performance-enhancing properties in lubricants, their adverse effects on emission control systems and the environment necessitate a careful balance. This has led to the development of low-SAPS (Sulphated Ash, Phosphorus, and Sulphur) lubricants designed to provide adequate protection and performance while minimising negative impacts.

Now you are all caught up…

So as you can see SAPS can be both good and bad. Often SAPS and indeed oil additives in general are treated as if they are some evil in the oil and although I have no innate feelings of sorrow for multibillion oil Goliath’s for the problems they may face, in terms of the formulation chemists in what they are being asked to achieve does feel unfair as often the requirements are directly opposing to each other.

For instance your typical family car you want:

• Oil you never have to change or maintain requiring the minimal servicing possible meaning it needs to be highly refined or synthetic to last for a long time, which means less solvency and with little to no natural wear protection.
• An oil that produces zero ash ruling out all but amine detergents, but requiring great dispersant properties at the same time to take all the emissions pumped back into the oil by exhaust gas recirculation.
• An oil that gives excellent fuel economy meaning it’s as thin as possible, but also plenty of wear protection despite the reduced antiwear additives requirements.

Engine life vs environment life

As with all things it’s often a choice. Whether you save the engine or the environment. Oil formulations today are more biased towards environmental protection than engine protection. For instance, low fuel consumption means your engine oil needs to be thinner and gives less surface separation and hence lower component life.

It’s all to do with how you balance things. Some decisions seem in total opposition to common sense at times. Take the majority of electric vehicles (EVs) you see on the road today as explained in the box below the choice on longevity of components appears to be a secondary concern.

The choice of EV manufacturers to have highly loaded mechanical components share the same fluid as the electrical components may seem strange to some including myself. This is because highly loaded mechanical components generally require sulphur based anti-wear additives and a thick lubricant with a high viscosity index (VI) for stable viscosity and wear protection. However electrical components want no sulphur as sulphur attacks copper wires and a very thin low VI oil to dissipate heat quickly. These are complete opposite requirements so you either pick a side and in most cases it’s the electronics meaning the loaded component life is much less than an equivalent on a non EV vehicle, or get a mediocre mix of both worlds with neither requirement being met.

So in the component life vs environment we need to be sensible in how we balance things. After all a typical EV will take around 7 years for the average driver before the greenhouse gases of production are offset by the benefits of less greenhouse gases from driving the engine. Equally a typical hybrid is about 10 years. These are quite long periods of time and even as we improve these processes to say 4 to 5 years let’s say, we need to ensure the engines we produce actually last significantly longer than this to get the benefit.

So this is why zero SAPS must only be done on the basis engine life can be maintained whilst doing so. Hence I prefer the iterative lowering approach which allows for small incremental improvements and tweaks to formulations tested over years of real world data before hurrying to zero SAPS lubricants when the engines and formulations are not yet there.

For example this data is from a medium sized heavy duty vehicle engine where a customer did some research on an engine with addition of ZDDP on bore wear increase vs a baseline level with different manufacturers oils. The finding was as expected increasing ZDDP content lowered the amount of wear as the tribological films stabilise more with higher levels of antiwear. Interestingly increasing the level in their instance over 2000 caused more issues with corrosion – note no additional additives were changed so you would likely tweak other additives to compensate for this in real life. Now for an increase in bore wear of about 1000 nm the customer found between 5% and 20% increase in oil consumption over a 6 week test bed period. However imagine this over the long term in that you could potentially over a couple years perhaps double the rate (that is an arbitrary number – don’t quote me on that) of oil consumption in which point the benefits of reduced ash are outweighed by the increase in oil used and indeed the premature failure of engines.

Clearly some much larger and detailed studies need to be done into this area to draw a definitive conclusion. A six week test bed is not a real world example and indeed you need data from likely thousands if not more of vehicles over years to get such accurate data. This is the type of information the real world sold engines to real drivers achieves, but if you are selling to the public you want small not large jumps in formulation changes. At the moment the iterative every engine generation lowering SAPS a little bit seems a much safer approach than the argued ban on SAPS entirely. Indeed we may find that e.g. X level of SAPS is the minimum a 4 stroke combustion engine can take in its current design and we stay at that level until new technologies of engines allow us to go further.

Conclusion Striking the Right Balance of SAPS

The key to harnessing the benefits of sulphated ash while mitigating its risks lies in balance. For gaseous engines, where the stakes are higher due to the lack of liquid fuel lubrication, selecting the right oil with an optimal sulphated ash content is critical. However, even for your average passenger car the level of SAPS is in the balance. It’s about finding that sweet spot – enough to protect and clean but not so much that it leads to deposits and emissions issues.

In conclusion, sulphated ash in engine oil is a crucial component. It plays a multifaceted role in protecting engine components, ensuring cleanliness, and neutralizing acids. However, its benefits are only realized when maintained in the right proportion. Like a skilled tightrope walker, the balance of sulphated ash content is essential for the high-wire act of engine performance and longevity. In the end, it’s all about achieving harmony in the complex symphony of engine operation.

Next time on Learn Oil Analysis?

Next time, actually let’s do it now. How is oil analysis related to all this?

Well it’s simple as we are putting more demands on our engines and lube oil formulations, gone are the days where an oil could take large film thickness drops and still be ok, or additive depletion and plenty reserve capacity. Modern formulations are as mentioned a tightrope with the slightest wobble potentially leading to catastrophic failure.

Oil analysis in this instance is your best chance to avoid disaster acting as your safety net to catch problems before your tightrope walker splatters on the ground.

With LubeWear acid digestion you can detect issues much much earlier than traditional oil analysis meaning the net is much higher and the fall can be smaller. Want to find out more then click contact us to get in touch.