Over recent years, it’s been easy to imagine the demise of the simple two-stroke engine. The technology, once a mainstay in a variety of small-engine-powered vehicles and handheld equipment applications, is now often displaced by increasingly compact four-cycle engine designs and electrification.

Why has this happened? The short answer is that two-stroke engines have been an easy target for tightening emissions regulations around the world. And not without reason: two-cycle engines have comparatively higher emissions versus other modern small engine technology. Because their exhaust and intake ports are open at the same time, two-cycle engines allow about 30% of unburnt combustion gases to exit the exhaust on every power cycle. As well, they consume a significant amount more fuel and oil over the same duty cycle versus comparable four-stroke technology.

But ask some major original equipment manufacturers (OEMs), they will tell you that two-stroke technology is not going away. Instead, new investments are being made to make it cleaner, more efficient and effective for professionals who require highly reliable equipment. These new developments have critical implications for lubricant technology that enables such equipment to meet its full potential. Here’s a look at what’s happening and what it means for oil marketers:

The Case for Two-Cycle Engines

While there are downsides from an emissions standpoint, two-cycle engine technology has some major advantages versus the types of technology being used to replace it. Because the designs are simpler and feature fewer moving parts, two-cycle engines are easier to maintain and care for—a characteristic with major appeal to busy professionals and hobbyists. They also provide desirable horsepower in a compact lightweight package.

Comparably, electric and four-cycle technology features some downsides that have not yet been overcome:

• Electric engines are not attractive for professional applications. While battery-powered lawn and garden equipment is often sufficient for the average homeowner, the professional landscaping industry requires tools that deliver all-day power. Presently, electric technology does not offer the power or longevity required for certain professional service.
• Four-cycle engines can be too heavy for many handheld equipment types. Bigger and featuring more moving parts, four-cycle engines are less attractive for handheld equipment such as chainsaws, trimmers, blowers and others. By contrast, two-stroke engines feature a much more desirable weight-to-power ratio.

OEMs continue to develop four-cycle engine technology to meet the needs of applications that have traditionally applied two-cycle engines. But the fact remains that two-cycle engines still have an important role to play in a variety of popular applications—and it’s important to optimize the operation and emission profiles within these engines.

Cleaning Up Two-Cycle Engines

Two-cycle engines’ inherent advantages have led OEMs to look for new ways to lower emissions in such applications.

One of the primary ways this has been done is through the application of catalytic converters. A common feature in passenger car vehicles for many years, catalytic converters essentially convert undesirable emissions into water and oxygen. And for that catalyst to do its job, it must remain clean and free of poisoning the precious metal substrates or blockages.

The use of catalytic converters in small engine applications is not brand new, but an increasing worldwide focus on emissions reduction is accelerating adoption. And that has some implications for the types of lubricants that have been traditionally used in two-stroke engines.

The Need for Low-Ash or Ashless Lubricants

Because the lubricant gets mixed directly with the fuel in a two-cycle engine application, the composition of the lubricant can directly impact the performance and durability of the catalytic converter. Specifically, lubricants that are compatible with catalytic converters must be formulated with low or no ash content. Ash can have the tendency to plate out on the precious metal substrate within catalytic converters, which can lessen its effectiveness.

Our View

For two-cycle engine technology to remain viable and effective, the right lubricants need to be developed and used within the right applications to enable such equipment to meet the needs of end users reliably and efficiently. Low-ash or ashless lubricants must not only be available in the marketplace, but it is incumbent upon our industry to continuously educate end users on the importance of using the right lubricants for the right applications.

As global emissions standards continue to tighten, we anticipate a continued convergence of hardware and lubricant changes that will be required to meet changing regulatory thresholds. These are considerations that lubricant manufacturers everywhere must keep in mind as we move into the future. The right combinations of additive chemistry will become an increasingly vital component in lubricants for any and every application.