How many gallons are in a 35 lb jug of oil?

Quick Answer

There are approximately 5 gallons in a 35 lb jug of oil. This is determined by converting the weight of the jug (35 lbs) to volume using the density of oil. Most motor oils have a density around 7.1 lbs per gallon. By dividing the weight by the density (35 lbs / 7.1 lbs/gal) we get approximately 5 gallons.

Calculating Volume from Weight and Density

The weight of a fluid can be converted to volume by using its density. Density is defined as the mass or weight of a fluid per unit volume. For liquids like oil, density is commonly measured in pounds per gallon (lbs/gal).

To calculate the volume, we use the following relationship:

Volume = Weight / Density

– Volume is the amount in gallons
– Weight is the total weight in pounds
– Density is the density of the fluid in lbs/gal

So for a 35 lb jug of oil with a density of 7.1 lbs/gal, the calculation is:

Volume = Weight / Density

Volume = 35 lbs / 7.1 lbs/gal

Volume = Approximately 5 gallons

The density value of 7.1 lbs/gal used here is typical for motor oils like 5W-30. Other types of oils may have slightly different densities, which would alter the final gallon calculation.

Typical Densities of Common Oils

Here are approximate density values for some common types of oils:

Oil Type Density (lbs/gal)
Motor oil (5W-30) 7.1
Motor oil (10W-30) 7.3
Motor oil (synthetic) 7.0
Vegetable oil 7.7
Mineral oil 7.5

As shown above, motor oils tend to have densities in the 7.0-7.3 lbs/gal range. Vegetable and mineral oils are slightly higher at around 7.5-7.7 lbs/gal. These minor differences in density lead to small variations in the final volume calculation.

Always check the product label or specifications to find the exact density if available. If the density is unknown, the above values can be used as reasonable estimates for the oil type.

Converting Other Weights of Oil to Volume

The same method of using density to calculate volume can be applied to oil containers of any weight. Let’s look at a few examples:

1. A 5 lb jug of motor oil (density = 7.1 lbs/gal)

  • Volume = Weight / Density
  • Volume = 5 lbs / 7.1 lbs/gal
  • Volume = 0.7 gallons

2. A 55 gallon drum of synthetic oil (density = 7.0 lbs/gal)

  • Volume = Weight / Density
  • Volume = 55 lbs / 7.0 lbs/gal
  • Volume = 7.9 gallons

3. A 500 ml bottle of vegetable oil (density = 7.7 lbs/gal) * 1 gal = 3785 ml

  • Volume (ml) = 500 ml
  • Convert to gallons: 500 ml x (1 gal / 3785 ml) = 0.13 gallons
  • Weight = Volume x Density
  • Weight = 0.13 gal x 7.7 lbs/gal = 1 lb

So the 500 ml bottle weighs approximately 1 pound.

These examples demonstrate how to convert between weight and volume for any size container of oil using the oil’s density. This works for very small volumes like 500 ml up to large 55 gallon drums.

Factors Affecting the Density of Motor Oil

The density of motor oil can vary slightly depending on factors like temperature and oil formulation. Here is more detail:

Temperature – As temperature increases, the density of oil decreases very slightly. This is due to thermal expansion of the oil molecules as heat is applied. The effect is small, but measurable. Expect a decrease of around 0.0006 g/ml (0.005 lb/gal) for a temperature rise of 100°F.

Oil Formulation – The specific composition of the oil including base oils used and additives added can result in small density differences. As a general rule, higher viscosity motor oils have slightly higher densities. For example, a 10W-30 oil may have a density 0.1-0.2 lbs/gal higher than a 5W-30 oil. Synthetic oils tend to have lower densities than conventional oils.

Age and Use – As motor oil is used and ages, some slight evaporation and loss of lighter fractions can occur. This leads to a gradual increase in density over time. The effect is small over normal oil change intervals. But oils analyzed after very long use can show density increases of 1-2%.

Since these factors are relatively minor, using the nominal new oil density values is appropriate for most volume calculations. But the slight variability does demonstrate the importance of using actual measured oil density data when extreme precision is required.

Estimating Volume in an Irregularly Shaped Container

In some cases, oil may be packaged in an oddly shaped container that makes it difficult to calculate a precise internal volume. For example, consider a 5 lb plastic jug with irregular curves. In this scenario:

  • Weigh the full container to get the total weight of oil.
  • Estimate the internal volume based on physical dimensions or by measuring how much water it displaces.
  • Calculate density as Weight/Estimated Volume.
  • Use the derived density to find volumes for other fill levels.

Let’s assume we measured the irregular 5 lb jug to be around 1.25 gallons in volume. The calculated density is then:

Density = Weight / Estimated Volume

Density = 5 lbs / 1.25 gallons

Density = 4 lbs/gallon

We can now use this density to find the volume at other weights:

2 lb weight -> Volume = 2 lbs / 4 lbs/gal = 0.5 gallons

7 lb weight -> Volume = 7 lbs / 4 lbs/gal = 1.75 gallons

By taking the extra step to determine the density, we can find the volume for any fill level despite the irregular shape.

Effects of Temperature on Oil Volume in Storage

When oil is stored in large heated tanks, temperature changes can cause the volume to expand or contract slightly. This needs to be accounted for when measuring the exact amount held in the tanks.

As the oil gets warmer, the volume increases due to thermal expansion. The effect is approximately:

– 0.1% volume increase for each 15°F rise in temperature

Conversely, as the oil cools down, the volume decreases at the same rate.

This volume change can have a small but significant effect, especially for tanks holding thousands of gallons of oil. A 50°F temperature swing could alter the volume by 0.5% or more.

To ensure accurate inventory measurement in tanks, temperature sensors are installed to monitor the oil. Volume readings from level meters are then compensated mathematically to account for the thermal expansion or contraction. This provides consistency regardless of current temperature conditions.

Small storage containers experience less noticeable volume changes from temperature swings. But the effect should still be recognized when precision is important.

Common Questions

How many quarts are in 35 lbs of oil?

With oil at a density of 7.1 lbs/gal and 4 quarts per gallon, 35 lbs of oil is equivalent to:

35 lbs / 7.1 lbs/gal = 5 gal
5 gal x 4 quarts/gal = 20 quarts

So 35 lbs of oil is approximately 20 quarts.

How much does one gallon of motor oil weigh?

Using the nominal density of 7.1 lbs/gal for motor oil, 1 gallon weighs 7.1 lbs.

This may vary slightly between brands and formulations but serves as a good average.

How can I find the density of an oil if it’s not labeled?

A few ways to determine density if it’s unknown:

– Weigh a measured volume of the oil and calculate density = weight / volume

– Use a density measurement tool like a hydrometer

– Look up oil density values for that type of oil

– Contact the manufacturer/supplier to get typical density ranges

Knowing the exact density allows accurate volume calculations from any weight.

How much does a 5 liter jug of synthetic oil weigh?

With synthetic oil at around 7.0 lbs/gal density:

– 5 liters = 1.32 gallons

– 1.32 gal x 7.0 lbs/gal = 9.2 lbs

So a 5 liter jug of synthetic motor oil weighs approximately 9.2 lbs.


By using the density of oil, we can convert between the weight and volume of any container or tank. A 35 lb jug of typical motor oil with a density of 7.1 lbs/gal contains about 5 gallons. The minor differences in oil densities due to factors like temperature, age, and formulation create small variations in this calculation. But using the nominal densities provides sufficient accuracy for most applications. Converting between weight and volume allows inventory tracking, fluid transfer, and other activities to be carried out reliably for oils.

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