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Oil High Viscosity Flow Meter

How are oil and other high viscosity liquids measured?

For industrial type applications, oil and other viscous media can be measured by a flow meter. The flow meter is installed inline with the process piping and can calculate the rate of flow using different technological principles of operation.

Why is measuring and monitoring oil different than other media types?

Oil has a higher viscosity than many other liquids. Certain flow meter technology types are not compatible with the viscous nature of oil.

What is liquid viscosity?

Liquid viscosity is a property of fluid dynamics and can be explained most simply as the inherent properties within the media that determine the resistance it has, within itself, to flow.

A simple example would be water versus maple syrup. When you overturn a glass of water, it comes out quickly. When you overturn a jar of honey or maple syrup, you must be patient before it hits your pancakes. The rate at which the liquid can move downward is partly determined by the liquid viscosity.

It can also be described as the internal friction within the liquid. In other words, how apt are the molecules to move away from each other without clinging to each other (or to surfaces in contact with the liquid)?

Does it matter what type of oil it is for the flow meter?

Absolutely. Different liquids have different viscosities which dictate which type of flow meter might be best for the application. Certain flow meter technologies are suitable for lighter oils, but not for heavier ones. It is important to know the cP or cSt of your media. Flow meters will generally have a specified maximum viscosity rating.

High viscosities cause less laminar flow profiles as the flow of the media in contact with the pipe walls will be much slower than the flow in the middle of the pipe due to the media “clinging” to the side wall. It can also create other unintended effects for certain flow meter technologies that could directly affect the flow meter’s accuracy.

There are flow meter technologies, like positive displacement, where you should not use liquids that do not meet the minimum viscosity requirement for the meter. The mechanical principle of operation is protected by viscous liquids that essentially “grease” the moving parts, reducing friction that leads to significant wear within the gears of the flow meter. PD meters are not suitable for low viscosity liquids with no lubrication properties, like water.

Which are the technology types for oil flow meters?

There are a few technology types that are compatible, in principle, with oil measurement. Depending on certain application variables and the level of viscosity of the media, certain technologies may not be suitable for a particular application, even if they are suitable in general.

Positive Displacement Oval Gear Oil Flow Meters

Turbine Oil Flow Meters

Coriolis Oil Flow Meters

Rotameters for Oil (Variable Area Flow Meters)

Ultrasonic Oil Flow Meter

Differential Pressure Oil Flow Meter

Which flow meter technologies are not suitable for oil and other viscous media?

There are flow meter technologies that are not compatible with oils or other viscous media.

  • Magnetic
  • Oscillation
  • Paddle/Flap/Target Types
  • Paddle Wheel and Pelton Wheel
  • Vortex
  • Thermal Mass
  • Thermal Dispersion
  • Rotameter – unless viscosity compensated
  • Ultrasonic – unless viscosity and temperature compensated

Can magnetic flow meters measure oil?

No, magnetic flow meters are not typically suitable for measuring oil flow. This is due to the fundamental principle on which these meters operate. Magnetic flow meters rely on Faraday's law of electromagnetic induction to measure flow, which requires the liquid passing through the meter to be electrically conductive.

Oil, in general, is a non-conductive liquid. Since it does not conduct electricity, it does not create a measurable voltage when flowing through a magnetic field. This is essential for the operation of a magnetic flow meter.

What is the best flow meter for grease?

The best flow meter technology for grease is positive displacement. Many of the other flow technologies that can handle media that is less viscous will not function properly with higher viscosity media.

What is the best flow meter for lube oil?

Depending on the viscosity of the lube oil and other application parameters there are more flow meter technology options available for lighter oils like lube oil. Our ultrasonic, rotameter, and turbine flow meters are generally compatible and cost less than the other couple of oil flow meter technology options.

A great option is our DUK Inline Ultrasonic Flow Meter

What is the best flow meter for crude oil?

If the crude oil application is for large pipe diameters with higher flow rates, A clamp-on flow meter like the KOBOLD DUC Clamp-on Ultrasonic Flow Meter is a great option. Most other oil flow meter technologies mentioned here are available for smaller pipe diameter applications.

What are mechanical oil flow meters?

Almost all types of flow meter technology typically used with oil and viscous fluids will be mechanical in nature. This means that there are generally moving parts involved in the principle of measurement. Non-mechanical flow meter options for oil include Ultrasonic and Differential Pressure.

What are the advantages of using oil flow meters?

  • Monitoring and Controlling Fuel Consumption: Fuel oil flow meters help in tracking the amount of fuel being used by a system or machinery. This is crucial for managing operational costs, especially in industries where fuel consumption directly relates to production costs.
  • Efficiency Optimization: By monitoring fuel flow, operators can identify inefficiencies in the system, such as leaks or irregular consumption patterns, and take steps to optimize performance.
  • Regulatory Compliance and Environmental Considerations: In many industries, there are regulations regarding fuel usage and emissions. Accurate measurement of fuel oil flow is essential for compliance with these regulations and for minimizing environmental impact.
  • Preventive Maintenance: Regular monitoring of fuel flow can help in identifying potential issues in the system, allowing for preventive maintenance before significant problems occur.
  • Safety: In some systems, especially where high volumes or high-pressure fuel is used, monitoring fuel flow is vital for safety reasons, to prevent over-pressurization and ensure the system operates within safe limits.

Do oil flow meters include an oil flow switch?

Yes, some do as an integral part of their design build. Some even offer more than one switch point. Some flow meters do not offer any. It is dependent on the flow meter model.

Here are some rotameter oil flow meter options that also offer an integral switch.

How do I choose an oil flow meter?

Choosing a flow meter can be a very daunting task. There are a wide variety of considerations that apply to choosing a flow meter for any application. For oil flow meters, the additional consideration is not exceeding the recommended maximum viscosity of the flow meter. To learn more about all the other variables in choosing a flow meter, visit our article on How To Choose a Flow Meter which provides a thorough list to begin your flow meter selection process. Our team of technical experts is also happy to help you with your application at or 412-788-2830.

What flow meters are best for hot oil and other hot viscous media?

Many flow meters that are built for oil and other viscous media applications can handle higher temperatures. Each individual flow meter model, based on the material build and the placement of the electronics, will state a maximum temperature. Here are some max temperatures for KOBOLD Oil Flow Meters.

Is a hydraulic flow meter different than a flow meter for oil?

While both terms indicate that the media going through the flow meter has a higher level of viscosity, the term hydraulic generally indicates that there is also a higher pressure present in the line/process.

Visit our article on hydraulics and pneumatics to learn more.

Maintenance and calibration of oil flow meters

To guarantee accuracy and longevity, regular maintenance and calibration of flow meters is indispensable. This includes routine checks for wear and tear, recalibration to ensure continued accuracy, and cleaning to prevent any buildup affecting measurements. KOBOLD’s flow meters are designed for ease of maintenance, ensuring they remain a reliable part of your operations for years.

Visit our article on flow meter calibration to learn more.

Oil flow meter manufacturers

KOBOLD proudly offers a wide variety of oil flow meters in a variety of flow meter technologies including rotameter/variable area, positive displacement, Coriolis, ultrasonic, and turbine. Our team of expert engineers is available for free to guide you through the process of selecting an oil or high viscosity flow meter at 412-788-2830 and

Featured Products
Oval Gear Positive Displacement Flow Meter
DON - Positive-Displacement Flow Meters

For Viscous Liquids | Up to 660 GPM | Up to 300° F | Up to 1,450 PSI | NPT or ANSI Connections | Batching and Totalizing | Bi-directional Capabilities | Top Seller

Viscosity Compensating Flow Meter and Switch
VKG - Viscosity-Compensating Flow Meter and Switch

Made in the USA | Direct Reading Oil Scale | For Higher Viscosity Media | Easy Installation | Up to 175 PSI | Up to 212 °F | NPT Threads | 0.03...21 GPM | Optional Switches

All-Metal Viscosity Compensating Flow Meter for Oils
VKM - All-Metal Viscosity Compensating Flow Meter and Switch

Made in the USA | Top Seller | 0.03...20 GPM | Patented Viscosity Compensation | Viscosities up to 540 cSt | Up to 5,000 PSI | Brass or Stainless


KOBOLD USA is a subsidiary of KOBOLD Messring GmbH, a world-leading instrumentation engineering business founded in Germany in 1980 by Klaus J. Kobold. With patented technology and superior service, the company quickly established itself as one of the global leaders in sensor and control systems with high quality products. The KOBOLD brand name became synonymous with superior quality and technological advancement in instrumentation engineering.

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