Engines and Fluids: A Winning Team Is Revealed

The world of spark-ignition (SI) oils was simple for many years. API Service Classification started with SA in the 1920s and recently reached SN, and new oils have always been made compatible with the previous versions. But recent changes warrant a closer look at this important fluid. Photo by U.S. Air Force Airman 1st Class Thomas Karol.

It often takes a team to properly perform all aspects of tree work. And, similarly, it takes a team of fluids when it comes to the proper lubrication and operation of the various engines that might be operating in performance of that tree work.

Let’s have a look at how to assemble a good team of fluids for those hard-working engines.

For clarification, we’ll be discussing fluids for the two engine types. The first is compression ignition (CI) – diesel, where air is compressed and gets so hot that when the fuel is introduced (injected), it burns without needing a spark plug to ignite it. The second is spark ignition (SI) – gasoline, where a spark is needed to ignite the fuel. Each of these combustion techniques generates different combustion temperatures as well as emissions byproducts, and each has its own special requirements of an effective oil.

Compression-ignition lubricating oil

Compression-ignition (CI) lubricating oil is a perennial favorite in tree care operations and is entrusted to do three simple things: keep moving components separated from each other, isolate contaminants and assist in heat transfer throughout the engine. Perhaps easier said than done some days.

With a nice pleasant color when new, it takes on a darker hue as it spends time in today’s diesel engines, where it is thrashed about and expected to last longer than ever before. A challenging task.

When making an oil selection, one should be looking for the latest API Service Category of CK-4, which is fully backward compatible with previous oils. Or, in those rare cases when the newer FA-4 is approved, substitution is acceptable. But do be certain that none of this FA-4 stuff, with its thinner dynamic viscosity (specifically HTHS, or high-temperature high sheer), is used in engines not specifically approved for its use, as it just doesn’t have the strength to protect them properly once fully warmed up. And note that the FA-4 is primarily approved at this time for newer, on-road engines only.

Next, be sure to select the proper viscosity, noting that multi-grades are most prevalent and often used year around. An example is a 15W40, a nice, thin 15 weight for speedy cranking, but acting nicely as a 40 weight once warmed up due to the additive packages that tighten things up. By the way, the “W” in between is simply a notation and does not suggest or validate “winter” use.

Some of the oils you might take a hankering to will be strictly petroleum based and some fully synthetic based, and some a blend of the two. The most crucial thing is to be sure it is the viscosity you need and that it has that API Approved label. And when the fluid has done its time and is worn out, be sure to send in a replacement. No one has ever been penalized for changing out the oil too often.

Spark-ignition (SI) lubricating oil

The world of spark-ignition (SI) oils was simple for many years. API Service Classification for oils started with SA in the 1920s. Over the years it moved to SB, SC, SD, etc., skipping only SI and SK. New oils were always made compatible with the previous versions. So it was just a matter of selecting the most current (automotive-based) category – now at “SN” – as that wonderful backward compatibility continues fully for these products.

At various times in history, there have been oils that met both the “C” (for CI) and “S” (for SI) categories – simplifying stocking needs for mixed-engine fleets – but these products are rare these days, and it’s straightforward to simply purchase a good product of each type.

Some trouble has come along in more recent years, though, with the introduction of emissions-control devices and, more specifically, that wonderful and delightfully simple three-way catalyst, which does not welcome zinc – more specifically the ZDDPs (Zinc DialkylDithioPhosphates) that had been used for many years because of excellent anti-wear characteristics. A familiar story. Such an unwelcome chemical tends to coat catalysts and reduce their effectiveness. So the good oil-development folks, along with the engine companies, have been teaming up to come up with blends that are effective overall, but with limited zinc levels, measured as parts per million (PPM).

All well and good for automotive-based engines that one might be using, as there is a full complement of oils available at a whole range of required viscosities. But when taking care of the smaller, air-cooled products, a different tactic might now be helpful. Rather than wading through all the automotive-based offerings – as has been common for just about forever – have a look at the offerings strictly for their smaller brethren. A couple of things strengthen the case for doing so.

One is that it’s easier and quicker to source an oil that will work properly. A second is that these are strengthened overall for the severe needs of these engines, which are dependent on the oil itself for cooling. A third is that zinc can readily be added back in, as the troubles of the catalyst are not there. And a final point is, it’s simpler, with all the many fluid containers scattered about a shop and work site, to quickly and confidently know that a particular product is made for these particular engines.

Petroleum diesel fuel

What a history for this stuff! At one time mostly a castoff from the refining process, petroleum diesel fuel is now widely used and drives so many of our products – and so much of the economy.

Engine Oil Categories

A major recent change has been the required adoption of ultra-low-sulfur diesel (ULSD) with a required sulfur limit of just 15 PPM. Limiting the amount of sulfur reduced the general unpleasantness of the exhaust and also allowed for the adoption of emissions after-treatment products utilizing catalysts, specifically selective catalyst reduction (SCR).

Early troubles with reduced lubricity – as sulfur works quite well in this regard – were long ago addressed with an enhanced-lubricity requirement, accomplished by the blenders with the addition of some “slippery” chemicals.

It is critical that this fluid remains as clean as possible before it is supplied to an engine, especially engines with a high-pressure common-rail (HPCR) injection system. The clearances and tolerances inherent in these are extremely close, and even quite small particles can cause substantial damage. It’s crucial that everyone dealing with ULSD understand this and adhere to very strict refueling-cleanliness needs of the engines.

Otherwise, this wonderful stuff that we can simply pull from the ground is doing quite well, thank you.

Bio-based diesel fuel

Oh, what an opportunity here! Indeed, as bio-based diesel fuel can actually be produced from various grains – soybeans, typically, in North America, and rapeseed in Europe – or from other “waste” products such as animal fats and, maybe in time, algae.

This is perfectly acceptable to put into play, typically up to a B20 blend, which is 20% biodiesel and the rest petroleum. Most engine companies seem accepting of this, though one is always cautioned to look at the specifics for each candidate engine. One is cautioned as well not to rely on too much of this if it will not be used fairly soon, because with the “food” aspect of the product, its shelf life is limited compared to a strictly petroleum product.

Current petroleum gasoline

Here’s another product for which life has gotten more complicated recently, and for which things are only going to get – well – even more complicated, as will be explained later.

Time was when gasoline was basically a single product. You could buy higher octane variations, of course, but the lowest pump price was often the major purchasing decision.

Things changed with the determination that MTBE (methyl tertiary butyl ether) was not a good oxygenate overall, as it contaminated ground water. Oxygenates, by the way, improve the gasoline-combustion process.

So here comes ethanol, a good oxygenate at levels up to 10%, and commonly used all over, especially in areas (primarily urban) where the air tends to be dirtier from all the vehicles on the streets.

All well and good. Overall, E10 (10% ethanol) is good stuff and has a good shelf life for automotive sorts of products. But not so well and good when it comes to small (air-cooled) engines. That is because the ethanol tends to separate out after around 30 days and attracts water, which consequently results in that unpleasant damage to carburetors that will then require service or replacement.

Users, be very aware! If the gasoline in one of these engines might not be used up within 30 days, add a fuel treatment at fill-up time. And if a particular container of gasoline is older or suspect, retire it to the comfort of a large tank on a vehicle and keep it out of the small engine completely.

Those of you who have access to E0 (0% ethanol), which is primarily in rural areas, should consider securing this stuff for your professional needs if possible. It could save you from some unwanted operational and repair expenses.

Comprehensive Engine Fluids Handling

Future petroleum gasoline

The somewhat new stuff now making its way to gasoline retailing sites all over is, of course, the mystical E15 (15% ethanol), a favorite for those in the business of producing ethanol and a concern for those knowledgeable about the appetites of engines. The Environmental Protection Agency (EPA) is now allowing year-round sales of E15, making it easier for a dispensing location to justify adding it to the menu.

Here there are two main areas of concern. The primary concern is that it is just not designed for running in small SI engines, so operational troubles and engine damage will occur. The second is that it’s actually against the law to use it in these engines (though it would likely be difficult to determine that someone is breaking this particular law). And a third concern – though maybe not as likely to actually occur – would be related to ethanol damage related to carburetors and the fuel system if it is left in place too long. After all, there’s just that much more ethanol – actually, 50% more. Those keen on buying E15 should limit their purchases to strictly approved automotive or truck needs.

Troubles at the fuel pumps are expected for the general population as, not surprisingly, the awareness of the limitations of E15 are not known by a majority of the population. So they don’t know not to buy it, especially if the pricing is attractive. For those relying on fluids to make a living, the trick is to be sure all employees know to stay away from this disagreeable stuff.

Air-based coolant

Air? In a fluids discussion? Well, yes, as air actually behaves as a fluid. And just because it doesn’t cost anything doesn’t mean we shouldn’t pay attention to it.

The key points are to keep any areas around engines relying on airflow both accessible and clean. Even a slight coating of debris on an engine surface or a radiator surface will have a significant effect on heat transfer.

When it comes to tending to them, it should be with moderate air or water pressure only. Common sense comes into play here. Don’t be attacking things with a pressure washer.

Liquid-based coolant

Selection of a coolant for today’s engines can actually be quite simple. You can use a traditional, inorganic-acid technology (IAT), the green stuff. Or you may need to use one of the newer organic-acid-technology (OAT) products, which are offered in a whole range of pleasing colors.

Both of these products are made from an ethylene (or sometimes propylene) base, then the inorganic or organic additives are blended in. The organic ones provide for a longer operational life, which is a welcome improvement.

Those of you who have been paying attention to the coolant world actually know there’s a third category – hybrid variations of the OAT products.

The point is to pay attention to the demanding needs of each of your individual engines. If the green IAT stuff is acceptable, well, great. It is easy to source and stock, and just know that you’ll need to change it more frequently.

If an OAT product is required, it’s best to select a fully approved one for a particular engine – which could actually be an OEM-only rather than an after-market product – and stick with it for the duration. It’s not necessary to be looking for some superstar product that is universal, as there are lots of products available, and each of the engine companies seems to have its own carefully developed game plan as to which additives are necessary for protecting their engines. This product really gets a workout and may be in that precious engine for a long time, so this is not an area in which to look for shortcuts. Pick some good coolant, and be sure to have an extra supply of it nearby for the engine.

Diesel-exhaust fluid (DEF)

This newest kid on the block has been left for last but deserves just as much attention as all the others on the team.

DEF is a simple concoction actually. It is just a fixed blend of urea (a product containing high levels of nitrogen with a primary use as a fertilizer) and water. What is made by one company is the same as made by another, if they’re following the ISO 22241 requirements. That’s basically it.

When sprayed into the exhaust stream of an engine with an SCR (selective catalytic reduction) system, a pleasant chemical reaction is accomplished that changes unwanted Nox (oxides of nitrogen, especially as atmospheric pollutants) into harmless nitrogen and water.

One might note that, as with any chemical reaction, one would like to ensure the reaction is as complete as possible. Therefore, the higher the touted “conversion rate,” the more effectively the reaction is being completed and the more Nox is being dealt with.

Buy this DEF from a trusted source. Don’t let an engine ever run out of DEF, as de-rating and shutdown will occur. Maybe keep a spare jug near any engine requiring it. And, if it’s necessary to transfer it into a tank with a funnel, be sure to only use one made of stainless steel or plastic.

The lineup is now complete

And here we are. The fluids team is in place. Treat them properly, and you’ll get years of performance and enjoyment from that valuable engine of yours.

John Fischer is an engine consultant based in Palatine, Illinois.

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