Heading 3403 covers preparations — meaning formulated products where the lubricating function is achieved by additives or blending, not pure mineral oils. Straight mineral lubricating oils without significant additive treatment generally classify in Chapter 27. If the product is a formulated blend with functional additives (anti-wear, anti-rust, emulsifiers), it is more likely to fall under 3403.

Cutting and metal-working fluids that function primarily as lubricants or cooling-lubricants can fall under 3403, but some water-based cutting fluids with a primary cooling function may classify elsewhere. The classification depends on whether the lubricating or the cooling function is principal, and on the product's composition. A binding ruling from CBP is advisable for borderline formulations.