An engine’s reliability depends largely on the quality of the lubricant working within it, particularly the viscosity level that develops when the unit operates for extended periods at full throttle and full load.
However, viscosity also affects fuel consumption, so it’s essential to find the right balance between protecting the mechanics and reducing energy consumption
The primary function of a lubricant within an engine is to separate the surfaces of interconnected mechanical components. Two examples of this are the pistons sliding within the cylinders and the bearings supporting the crankshafts, the so-called “bronze bearings.” In both cases, the oil must create a very thin film that prevents direct contact between the metal surfaces, despite the fact that they are subjected to strong pressure from repeated operating cycles. This must be proportionate to the workloads involved, which, in the case of heavy-duty earthmoving and agricultural machinery, those subjected to heavy and continuous operations, are particularly high.
The ability to adequately cope with these loads is greatly affected by the viscosity of the lubricants in use, a parameter that varies with temperature and, until recently, the higher the viscosity, the more engine protection it provided. However, this comes at the expense of efficiency, as high viscosity leads to energy absorption that penalizes power output and fuel consumption. It is therefore essential to always find the right compromise between the reduction of mechanical friction and engine protection, a balance that is all the more difficult to achieve the higher the working temperatures and the stresses involved.
Precisely to help technicians achieve this goal, the “Ht-Hs” (High Temperature High Shear) parameter was created. As its name suggests, it identifies the viscosity produced by the lubricant when operating at high temperatures. In the past, this parameter was measured through laboratory tests conducted at 100 degrees Celsius, but for engine oils intended for heavy-duty vehicles, it has recently been raised to 150 degrees Celsius.
This threshold, combined with measurements taken under high stress, precisely determines a lubricant’s ability to reduce fuel consumption without compromising engine protection. Typically, a lubricant with an “Ht-Hs” value of less than three and a half centipoises—the unit of measurement for viscosity—allows the engine to operate with low internal resistance and therefore with equally low fuel consumption. However, not all engines are compatible with this value, and therefore the use of lubricants recognized as having a low “Ht-Hs” must be approved by the vehicle manufacturers.
In this regard, the European Automobile Manufacturers’ Association introduced a specific technical specification in 2024, labeled “ACEAF01,” which identifies oils with “HT-HS” parameters between 2.9 and 3.2 centipoise and are therefore designed to meet the operating needs of the latest-generation heavy-duty diesel engines. It designates low-viscosity fuel-economy lubricants, thus ensuring maximum protection and minimal fuel consumption, as well as compatibility with the latest exhaust gas post-treatment technologies. Examples of specific lubricants for heavy-duty work vehicles aligned with the “ACEAF01” standards are those offered by the three Pakelo lines: “GoldenStar, “Excellence,” “Premium,” and “Regular,” depending on the base stocks used for the various formulations.
At the top of the range are the fully synthetic “GoldenStar La Plus” and “GoldenStar F-La Plus” lubricants, approved by nearly all major manufacturers of diesel engines intended for heavy-duty applications. “GoldenStar F-La Plus” oils are also certified “fuel economy” but are all based on “Low SAPS” technology, which ensures low levels of sulfated ash, phosphorus, and sulfur during operation, guaranteeing full compatibility with the current and most modern emission control systems required by various international regulations.
Titolo: Lubricant Pakelo: conciliatory balancing acts
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