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December 2, 2025

Motor-kettingzaag

How modern two-stroke and four-stroke engines evolve

For years, the differences between two-stroke and four-stroke engines were clear: two-stroke engines were known for their low weight and high power density, while four-stroke engines were quieter and more efficient. However, due to stricter emission standards, these characteristics have become more similar. The further development of both types of engines has blurred the classic boundary. For professionals in construction, forestry, landscaping, and industry, this has implications for the way machines are developed, maintained, and selected.
Emission standards as a driver of innovation

Since the late 1990s, stricter emission regulations have been implemented worldwide for small combustion engines. Machines such as chainsaws, brush cutters, generators, and pumps were subject to this legislation. Traditional two-stroke engines with fuel-oil lubrication could no longer meet the new standards, leading manufacturers to develop technical solutions.

Manufacturer-specific technical approaches

Each manufacturer has chosen its own approach. While all comply with the European Stage V emission standard, the applied strategies vary.

Manufacturer
Strategy
Core Technology
MakitaComplete transition to light four-stroke engine (MM4)Closed crankcase, splash and pressure lubrication, suitable for 360° operation
HusqvarnaImproved two-stroke engine (X-Torq)Separated scavenging flows, low emissions, up to 75% lower fuel consumption than standard two-stroke, high power
StihlImproved two-stroke engine with additional air channel (4-MIX)Oil-gasoline mixture with four-stroke-like combustion, up to 80% lower fuel consumption than standard two-stroke
HondaCompact four-stroke engine (GX series)Pressure lubrication, OHV, very low emissions, low vibrations
What does this mean for maintenance and lubricant choice?

The advanced engine technology brings different maintenance needs. Improved two-stroke engines from Husqvarna and Stihl are highly stressed and often operate at high speeds. Therefore, they require a high-quality two-stroke oil that provides sufficient protection under harsh conditions. A product like Eurol Super 2T Formax offers that protection and has a strong cleaning power, keeping exhaust ports and spark plugs clean. The cleaner and more efficient combustion this provides also results in low-smoke operation.

Compact four-stroke engines from Makita and Honda benefit from a full synthetic oil with a higher protection reserve. An API SL specification with increased zinc and phosphorus content contributes to extra wear protection of valves, camshafts, and bearings. Eurol Super Lite 5W-30 meets this specification and is excellent for such engines.

In addition, fuel quality plays a significant role. Euro 98 (E5) contains less ethanol than Euro 95 E10 and offers benefits such as:

  • Reduced risk of corrosion
  • Lower moisture absorption
  • More reliable starting after periods of inactivity
  • Less contamination in carburetors and injectors

For machines used seasonally, this difference is often noticeable.

The most suitable engine depends on the application

While emission standards have brought about a significant technological shift, the choice between two-stroke and four-stroke engines still depends on the working environment. Key considerations include:

  • The power-to-weight ratio
  • Vibration and noise levels
  • Amount of smoke produced
  • Maintenance ease and versatility

In forestry, a high power density is crucial, while in urban green management, noise levels may carry more weight. Technological advancements have expanded the possibilities, but the ultimate choice remains application-specific.