Lubricant price per liter or per kg: which should a quote use?

This comparison covers liquid lubricants and process oils sold in drums, intermediate bulk containers and bulk. Greases and pastes are normally sold by mass, and bulk custody transfer under a metering contract follows the measurement terms of that contract.

How do lubricant price per liter and price per kg differ?

Lubricant price per liter and price per kg differ in what they hold constant: a price per kg fixes the mass you pay for, while a price per liter fixes a volume whose mass depends on the oil's density and its temperature. Mineral and synthetic lubricating oils do not share one density. ASTM D1250-25 groups lubricating oils with densities from about 801.26 to 999.37 kg/m3 at 15 °C (ASTM International, 2025), so one liter of the densest oil in that group weighs about 25% more than one liter of the lightest (calculated from that range).

The table below decides which basis needs more information before two quotes can be compared.

The key row is the first: a per-liter price carries the product's density inside it, so the price per liter of a dense gear oil and a light hydraulic oil are not on the same footing. Comparing them needs the density of each.

When is a lubricant price per kg the better basis?

A lubricant price per kg is the better basis when the buyer compares different products, different suppliers or deliveries filled at different temperatures, because mass does not change with temperature or with the oil's density.

Price per kg also fits the way many plants account for material. Greases, pastes and concentrates are typically weighed. Gravimetric drum filling, where the filler stops at a target mass, gives a net weight that the buyer can check on a platform scale at receipt without any temperature correction. When a tender asks several suppliers for the same viscosity grade, their base oils and additive packages differ, so their densities differ too. Asking every supplier for a price per kg removes that difference from the comparison and leaves the real differences in price, package and terms.

A price per kg is weaker when stock, consumption or machine fills are tracked in liters. In that case the buyer still needs each product's density at 15 °C from the supplier's technical data sheet to translate kilograms back into liters for planning, and the quote should state that density beside the price.

When is a lubricant price per liter the better basis?

A lubricant price per liter is the better basis when the oil is delivered and invoiced by volume, such as bulk deliveries through a flow meter or tank deliveries measured by gauge, and the volume is corrected to a stated reference temperature. In that case the price matches the quantity the buyer can check on the delivery ticket.

ASTM D1298-24 describes density measurement as necessary to convert measured volumes to volumes or masses at the standard reference temperatures of 15 °C or 60 °F during custody transfer (ASTM International, 2024). ISO 91:2017 sets out the volume correction factors used to convert volumes measured at ambient conditions to reference conditions for transactional purposes (ISO, 2017). A per-liter price that names 15 °C as its basis therefore ties into an established measurement chain.

Price per liter also suits users who dose by volume, for example machine sumps and gearboxes with fill quantities in liters. The weakness appears when a per-liter price is quoted without a reference temperature or density: the buyer cannot tell how much oil, by mass, each liter represents, and cannot set that quote beside a per-kg quote from another supplier.

How do you convert a lubricant price per liter to price per kg?

You convert a lubricant price per liter to price per kg by dividing the price per liter by the oil's density in kg/L at the same reference temperature, normally 15 °C. To go the other way, multiply the price per kg by the density.

The worked example below compares two quotes for the same viscosity grade; every price and density in it is illustrative.

The key row is the third: on a per-kg basis illustrative Quote A costs 11.36 against 11.00 for Quote B, so A is the more expensive quote even though its per-liter figure looked close. Take density from the product data sheet or certificate of analysis. Use the density of the exact product quoted, not a typical value for the grade. If a data sheet gives density at 20 °C, ASTM D1250-25 notes that its metric procedures cover a base temperature of 20 °C in addition to 15 °C, so state which one you used.

Why does temperature change a lubricant's price per liter?

Temperature changes a lubricant's price per liter because oil expands as it warms, so a liter filled hot holds less mass than a liter filled cold, while the price per liter stays the same. Engineering ToolBox lists a volumetric expansion coefficient of about 0.0007 per °C for engine oil (Engineering ToolBox, n.d.).

At that coefficient, an oil filled at 35 °C occupies roughly 1.4% more volume than at 15 °C, so 1,000 L measured at 35 °C corresponds to about 986 L at 15 °C; these figures are illustrative and use the linear coefficient.

For drum and IBC purchases the effect is small per package but real across an annual contract, and it favors the seller when volumes are measured warm and not corrected. The fix is to agree that volumes are corrected to 15 °C using the ASTM D1250-25 or ISO 91:2017 correction factors, or to buy by mass, where temperature drops out of the comparison.

How much lubricant is in a 208-liter drum by weight?

A 208-liter drum of lubricant holds its nominal volume multiplied by the oil's density: at an illustrative 0.88 kg/L at 15 °C, 208 L is about 183 kg net. A denser oil at an illustrative 0.90 kg/L gives about 187 kg, and a lighter one at 0.85 kg/L gives about 177 kg, so the same drum size carries different masses.

Two more factors move the net figure. First, the fill temperature: if the 208 L is measured at a warmer filling temperature and not corrected to 15 °C, the drum holds slightly less oil by mass. Second, the fill level is set by the supplier, not by the drum. ISO 15750-2:2002 covers tight-head steel drums with a minimum total capacity of 212 L, 216.5 L or 230 L (ISO, 2002). A 208 L nominal fill is less than any of those capacities, so how full the drum is depends on the supplier's filling practice. Some suppliers fill to a volume, others to a target mass.

The net weight per drum therefore has to come from the supplier: ask for net kg per drum and the density at 15 °C on the quote, and check the net weight against the scale at goods receipt.

How do you compare lubricant quotes given in different units?

You compare lubricant quotes given in different units by converting every quote to one basis, normally price per kg, using each product's own density at 15 °C, and then comparing what each package actually contains.

Work through the quotes in this order:

1. Write down the unit and package of each price: per liter, per kg, per drum, per IBC or per bulk delivery.

2. Get the density at 15 °C for each product from its data sheet, and note the test method.

3. Convert per-liter prices to per-kg by dividing by density; convert per-package prices by dividing by net kg per package.

4. Check whether each per-liter price is at 15 °C or at the filling temperature.

5. Compare net content against the quantity you asked for: a quote for 40 drums of 180 kg is not a quote for 40 drums of 208 L.

Unit basis is only one reason two quotes do not line up. Delivery terms, package type, validity dates and minimum order quantities also move the comparison; the wider checklist is in why a chemical quote is not comparable to a competitor quote. Keep the converted figures with their densities in the comparison sheet, so anyone reviewing the decision can trace each number back to the quote.

How should a lubricant quote state its unit basis?

A lubricant quote should state its unit basis in full on every line: the price unit, the reference temperature for any volume, the density at 15 °C with its test method, the net content per package in both liters and kg, and any difference between the quoted and the requested quantity.

Use this checklist when you write or receive a quote:

• Price unit: per liter, per kg or per package, never left implied.

• Reference temperature: 15 °C for volumes, or 20 °C if both parties agree and the quote says so.

• Density at 15 °C and its test method, for example ASTM D4052-22 or ASTM D1298-24.

• Net content per package in liters and kg, and whether the fill is by volume or by mass.

• Conversion used, so the buyer can repeat it.

• Requested quantity against quoted quantity, with the reason for any difference, such as rounding to full drums.

A quote that carries these lines can be compared with any other quote without calling the supplier. Lubinpla's quote drafting states for each number the package and weight unit, the conversion and any difference from the requested quantity, and attaches a source and reference date to each value without calculating the price itself.