Navigating Engine Coolant Option

Engine coolants, often referred to as antifreeze, play a critical role in maintaining the optimal temperature of a vehicle’s engine. Choosing the right coolant is essential for preventing overheating, corrosion, and ensuring efficient engine performance. In this guide, we’ll explore the different types of engine coolants, their applications, and key considerations for making an informed selection.

Types of Engine Coolants

  1. Inorganic Acid Technology (IAT):

    • Composition: IAT coolants typically consist of ethylene glycol as a base fluid with inorganic additives such as phosphates, borates, and silicates.
    • Applications: Commonly used in older vehicles, IAT coolants provide basic corrosion protection but require more frequent replacement.
  2. Organic Acid Technology (OAT):

    • Composition: OAT coolants use organic acids, such as sebacate and 2-EHA, as additives along with a base fluid like ethylene glycol or propylene glycol.
    • Applications: Recommended for modern vehicles, OAT coolants offer extended service intervals, improved corrosion protection, and compatibility with various metals.
  3. Hybrid Organic Acid Technology (HOAT):

    • Composition: HOAT coolants combine the features of IAT and OAT formulations, using both inorganic and organic additives.
    • Applications: Suitable for a wide range of vehicles, including both older and newer models, HOAT coolants offer extended service life and robust corrosion protection.
  4. Silicate-free (Si-OAT) or Phosphate-free (P-OAT) Coolants:

    • Composition: Si-OAT and P-OAT coolants eliminate specific additives (silicates or phosphates) to address certain compatibility concerns.
    • Applications: Useful in vehicles with aluminum components, as they reduce the risk of silicate gel formation, preventing radiator and heater core clogging.

Key Considerations for Choosing Engine Coolants:

  1. Vehicle Compatibility:

    • Different engine materials (aluminum, cast iron, copper) may require specific coolant formulations to prevent corrosion. Always refer to the vehicle’s manual for compatibility guidelines.
  2. Service Intervals:

    • Consider the maintenance schedule of your vehicles. OAT and HOAT coolants generally offer longer service intervals compared to traditional IAT formulations.
  3. Temperature Range:

    • Engine coolants must effectively protect against freezing in cold temperatures and overheating in hot conditions. Check the recommended temperature range for your region.
  4. Additive Depletion:

    • Over time, additives in coolants deplete, affecting their protective properties. Regularly check and, if needed, replace the coolant based on your vehicle’s maintenance schedule.
  5. Environmental Impact:

    • Some coolants are formulated to be more environmentally friendly. If this is a concern, look for biodegradable or non-toxic options.

Tips for Selecting Engine Coolants:

  1. Follow Manufacturer Recommendations:

    • Always refer to the vehicle manufacturer’s guidelines for the recommended coolant type and service intervals.
  2. Consider Vehicle Age:

    • Older vehicles may have specific coolant requirements. It’s crucial to choose a coolant that aligns with the needs of your specific vehicle.
  3. Understand Coolant Color:

    • Coolants come in various colors (green, orange, pink, blue). The color often indicates the type of additives used. Consult your vehicle manual to decode coolant colors.
  4. Antifreeze-to-Water Ratio:

    • Diluting coolant with water is essential, but the ratio can impact performance. Follow manufacturer recommendations for the correct antifreeze-to-water ratio.
  5. Seek Professional Advice:

    • If uncertain, consult with automotive professionals or coolant distributors. They can provide insights based on your specific vehicle and operational conditions.

Why Choose Twin Specialties Corporation

Twin Specialties Corporation, a leading lubricant and coolant distributor, offers a wide range of products from reputable manufacturers such as Peak, Shell, and others. Their experienced team can assist purchasing managers, maintenance managers, and fleet managers in selecting the most suitable engine coolant for their specific needs. Whether you require a high-performance OAT coolant or a specialized Si-OAT formulation, Twin Specialties ensures access to top-quality products and expert guidance.


Selecting the right engine coolant is crucial for maintaining the health of your vehicles and preventing costly repairs. Understanding the differences between IAT, OAT, HOAT, and specialized formulations allows for informed decision-making. For further assistance and to explore a diverse range of engine coolants, contact Twin Specialties Corporation. Trust in their expertise and the quality brands they offer to keep your fleet running smoothly.


What is DEF?

DEF Defined & EPA Requirements

DEF, also known as Diesel Exhaust Fluid, is an aftertreatment fuel system liquid that is used in diesel engine vehicles to reduce air pollution. Specifically, DEF is designed to reduce the concentration and emission of nitrogen oxides (NOx), by converting nitrogen monoxide (NO) and nitrogen dioxide (NO2) molecules into:

  • Harmless nitrogen molecules, which are the most abundant in our atmosphere
  • Water
  • Carbon dioxide, which is harmless to humans, but still plays a role in climate change

By transforming harmful emissions into harmless gases, DEF plays a key role in reducing emissions over the past few decades. The 2010 EPA Emission Requirements for diesel engines are:

  • 0.2g/HP-hr of NOx
  • 0.1g/HP-hr Particylate Matter

Looking at the chart to the right, DEF has helped reduce emissions by 98% since the late 1980s. This has led to a cleaner environment with less “black” fuel exhaust. These results have made DEF and essential fluid for all diesel engine vehicles.

Ingredients & DEF Standards (ISO 22241)

Sometimes to solve complex problems, all you need is a simple solution. DEF is a simple product consisting of only 2 ingredients: urea and deionized water. With such a short ingredient list, why would it be tough to manufacture DEF? In order for DEF to work effectively and protect your engine and fuel system, DEF must be made with extremely pure urea and water. These purity requirements are clearly defined in ISO 22241, Diesel Engines – NOx Reduction Agent, Aqueous Urea Solution (AUS 32). Additionally, DEF products that meet ISO 22241 may be licensed to display the API DEF Certification.

What requirements are needed to meet the ISO 22241 standard? Each ingredient has the following requirements:

  • Technically Pure Urea with traces of biuret, ammonia, and water only. Urea that is free of aldehydes or other substances such as anticaking agents. The urea is to be free of contaminants such as sulfur, chloride, nitrate, or other compounds.
  • Water with very low inorganic, organic, or colloidal contaminants. This is achieved by single distillation, deionization, ultra-filtration, or reverse osmosis.

Using these purified ingredients, DEF must have a urea concentration of 32.5%. This ensures that enough urea is present to convert the NOx and ensures reliable operation of the selective catalytic reduction (SCR) systems. It is also the concentration that produces the lowest freezing temperature of 12 F. If the fluid does not meet these ISO 22241 standards, it cannot be classified or called a diesel exhaust fluid.

How does it Work?

Now that we have found the fluids needed to convert the NOx, we need the technology and equipment to catalyze those chemical reactions. The most common systems used are Selective Catalytic Reduction systems (SCR). The SCR allows the following chemical reaction to occur:

  1. Water evaporates and urea decomposes into ammonia and isocyanic acid
  2. Isocyanic acid reacts with the water vapor and hydrolyzes into carbon dioxide and more ammonia
  3. In the presence of oxygen and a catalyst, ammonia reduces NOx into nitrogen and water

SCRs have proven to be the most effective solution in reducing NOx emissions. SCRs are the only solution that curbs emissions without compromising fuel efficiency and engine performance. As an aftertreatment system, a system that does not work within the engine, SCRs allow engineers to tune engines that can help performance and efficiency. All diesel vehicles produced today have some sort of SCR built in.

SCRs also have safeguards in place to ensure a diesel engine is not operating without a proper amount of DEF. Many vehicles have warning systems to warn operators to refill their DEF tanks. If those fail, engines will shut down and will not engage until there is a sufficient amount of DEF in the tank to reduce any NOx produced by the engine. It is important for operators to monitor the DEF tank just like they would their fuel tank.

Benefits and Costs of DEF

With increased fuel efficiency, many fleets are noticing around a 5% fuel savings compared to older models. Off-road vehicles and equipment that use SCRs and DEF can see fuel savings well beyond 5%. With large fleets, that 5% can add up significantly over many vehicles and miles.

The DEF needed to properly reduce NOx is generally 2-6% of a vehicles fuel consumption (e.g. 2-6 gallons of DEF needed for every 100 gallons of diesel fuel consumed). To figure out your DEF needs, simply determine: miles driven by your vehicle, miles per gallon (MPG), and DEF dosing rate (2-6%). By dividing miles driven by the MPG, you find your fuel consumption. Multiply your fuel consumption by the dosing rate to get your required DEF volume.

The cost of the DEF is the only extra cost to SCR systems, but those costs can easily be offset (and then some) with the 5% fuel savings. The weight of a full DEF tank is only 5-9 lbs., which is negligible in large commercial vehicles. In passenger cars with diesel engines, typically you need to fill your DEF tank at each oil change. Fortunately, a 2.5-gallon container of DEF can be found for under $20 at most retailers.

Storing and Handling DEF

DEF has a freezing/crystallization point of 12 F. As DEF freezes into a crystalline slush, its volume can expand as much as 7%. Many vehicles have heating elements that ensure in-tank DEF does not freeze or threaten vehicle failure. Freezing does not affect the efficacy of the product, but it is important to store it in tanks at appropriate temperatures.

The shelf life of DEF is about 1-2 years, but could be reduced if the fluid is exposed to direct sunlight or stored at temperatures above 86 F. The water can evaporate in tanks, so it is important to keep the tanks sealed and at an ambient temperature around 75 F. If the fluid evaporates, do not add your own mixture as that can upset the precise chemical balance of manufactured DEF.

Where to get DEF

For commercial fleets and clients, speak with a distributor about solutions and certified products. Twin Specialties offers DEF in drums, totes, and bulk. Additionally, we can work with certain businesses interested in buying larger amounts of retail/consumer-packaged DEF products. Individuals who drive a diesel-engine vehicle can purchase bottles or DEF at gas stations, hardware stores, or auto shops. As diesel-engine vehicles become more popular, especially in Europe, many gas stations are adding AdBlue pumps where drivers can pump DEF directly in their car from the pump for cost savings.