As an OEM Technical Services Manager for Shell Lubricants, one of my primary responsibilities is working with vehicle and engine manufacturers as well as fleets to ensure proper coolant application. This includes troubleshooting problems, determining the need for new products, and evaluating product applications for the heavy-duty transportation industry.

We have seen that as diesel engines and component materials evolve, coolant technology must follow suit. In particular, the increased use of aluminum in modern engines has made changes to coolants necessary. However, a lingering misconception is that all coolants are the same and interchangeable with each other. Not using the proper coolant can lead to problems with the cooling system of a truck.

There are two distinctly different types of coolant. The first is older conventional fully formulated, or inorganic acid technology (IAT) and the second is new extended life coolant (ELC) with organic acid technology (OAT). Each coolant type protects engines from corrosion differently and thus, when different types of coolants are mixed, both are diluted, and their effectiveness can be significantly reduced.

The primary difference between fully formulated coolants and extended life coolants is the length of time and/or miles driven that each will remain fully effective. IAT additives in conventional coolants are sacrificial and will be consumed as they provide corrosion protection. While OAT additive ELCs last much longer and offer significant maintenance cost savings over the life of the coolant.

Below is some information about different coolant types.

  • Fully Formulated Coolants contain silicate and other inorganic additives, which along with supplemental coolant additives (SCAs) provide engine and cooling system protection. They offer a stabilized, low-silicate formula that helps reduce deposits and the risks of hard water scale. Fully formulated coolants typically contain nitrite and often molybdate to prevent corrosion damage which can result from cavitation pitting in heavy-duty diesel cylinder liners. Fully formulated coolants can provide protection for up to 200,000-250,000 miles or two-three years in heavy-duty applications under normal operating conditions. The user must monitor the condition of the coolant and make regular additions of SCAs to maintain additive levels.
  • Extended Life Coolants offer complete cooling system component protection and contain no silicates. They help to reduce water-pump failures, hard-water-scale deposits and silicate gel (the green goo you often see). They utilize organic additive technology and have the addition of nitrite and molybdate that protect cylinder liners from pitting corrosion damage. ELCs help reduce maintenance costs and improve water pump life, as well as eliminate the need for costly supplemental coolant additives. Shell Rotella ELCs are formulated to provide high performance protection for today’s heavy-duty diesel engines. They offer effective heat transfer, freeze and boiling protection, as well as corrosion protection for the cooling system. ELCs are designed to go 600,000 to 1,000,000 on-highway miles and even beyond with proper monitoring.
  • Nitrite Free ELCs are formulated to meet more severe operational conditions of modern, hotter-running engines. Nitrite free coolants provide improved protection of aluminum components including modern brazed aluminum heat exchangers and meet many of the latest OEM specifications. The versatile formulation may also be used in fleets that include passenger cars and light-duty trucks. The coolant is proven for extended life operation in medium and heavy-duty diesel, gasoline, LNG and natural gas vehicles and engines. (ELC NF) offers outstanding heat transfer that is superior to conventional coolants. The coolant has an extended life capability – up to 1,200,000 on-highway miles or 24,000 hours in Class 8 trucks1 and up to 600,000 miles or 12,000 hours in other commercial applications.

If different coolants have been mixed or the coolant is out of the correct specification, it doesn’t always mean that the coolant has to be drained and the entire system refilled, which can be a dozen gallons or more for larger vehicles. Shell Rotella ELC Concentrate will allow technicians to bring the coolant mixture to the recommended level. A freeze point correction chart for coolants will show how to adjust the coolant so that it is at the proper freeze point.

Here are some tips to keep in mind about coolant:

  • It is a good practice to check the coolant every time you change the oil or conduct preventive maintenance.
  • Drivers may want to consider carrying a gallon of the proper premixed coolant for their truck while on the road.
  • Remember, don’t mix coolants. IAT and ELC protect your engine from corrosion differently.

Shell Lubricants has test strips that allow the user in the field to check to make sure the level of OAT additives in their coolant is adequate for corrosion protection.

Shell Rotella also has ELC correction fluids which are used to restore additive content to recommended levels. These procedures enable you to bring your equipment’s coolant back to the proper specification without draining the entire cooling system. For additional information on coolants, visit

1 Requires full use of Shell Rotella® ELC Nitrite-Free 50/50 Coolant + Antifreeze in the system and proper maintenance. Proper maintenance as detailed at Follow OEM recommendations for specified maintenance.

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