2710.20.10.15 - Containing not more than 500 ppm of sulfur

This HTS category encompasses specific types of distillate and residual fuel oils that meet particular technical specifications. To be classified here, the fuel oil must test at 25 degrees API or more and possess a Saybolt Universal viscosity at 37.8°C ranging from 45 seconds to 125 seconds. This viscosity range aligns with the characteristics of No. 4-type fuel oils. The primary constituent of these oils must be petroleum oils or oils derived from bituminous minerals, with these oils forming at least 70 percent by weight of the product.

The defining characteristic for this specific classification is the sulfur content. This category specifically covers those fuel oils containing **not more than 500 parts per million (ppm) of sulfur**. This is a crucial distinction from its sibling category, 2710.20.10.25, which covers similar fuel oils that contain **more than 500 ppm of sulfur**. Therefore, the precise sulfur concentration is the key differentiator for customs classification at this level.

As this is a leaf node within the HTS structure, there are no further subcategories to introduce. The classification is determined by the physical and chemical properties described, namely the API gravity, Saybolt viscosity, and sulfur content. This level of detail ensures precise identification for trade and regulatory purposes, distinguishing these lower-sulfur fuel oils from their higher-sulfur counterparts.