Should Oil and Coolant Analysis Be Done Together?

With a large fleet, it is important to regularly assess equipment conditions and plan maintenance schedules to prevent breakdowns and maximize up-time.

Just as oils and coolants work together to keep fleets running smoothly, oil and coolant analysis work together to prevent premature wear and engine failure. If these fluids aren’t doing their jobs, fleets can’t do their jobs either.

Today’s heavy-duty diesel engines place much higher demands on the cooling system, which needs to absorb heat transferred from the engine, transmission, and hydraulic fluids. This has dramatically changed cooling systems and made monitoring them increasingly more important

In fact, it is estimated that half of premature engine failures are associated with problems in the cooling system. Yet the cooling system is not well understood and is often neglected.

While oil analysis is an invaluable condition monitoring tool, it does little to pinpoint issues in the cooling system. For that reason, it is important to conduct oil analysis and coolant analysis together. This will keep all systems – the engine, transmission, and hydraulics – running smoothly. Here’s how:


Oil and coolant analysis help identify many potential engine issues. High coolant temperatures can cause high oil temperatures, reducing the oil’s viscosity and lubricity. This leads to oil degradation, oxidation and eventual engine wear that can result in sticking rings and piston varnish.

Oil analysis can identify contamination caused by leaky head gaskets and air intake issues that can lead to unnecessary engine wear while coolant analysis can reveal chemical reactions occurring in the cooling system that warrant close attention. A significant drop in pH drops can indicate an air leak from a defective pressure cap or show that corrosion and dirt are plugging cooling system passages.


Monitoring coolants is also important to transmission life. High coolant temperatures allow other fluids to degrade which leads to reduced oil viscosity, and ultimately, transmission disc slippage. The slippage then generates heat and leads to oil oxidation – and the cycle continues. For the health of your transmission, it is important to analyze your coolant.


Hydraulic pumps and motors are less efficient when forced to operate at higher temperatures, due to lower viscosity and oxidation which may reduce the life of valves, pump slippers, barrels and plungers, and seals.

Test Both Conventional and Extended Life Coolants

It’s important to test both conventional and extended life coolants because formulation alone cannot prevent or correct the mechanical issues or chemical reactions that reduce cooling system performance.

Air and combustion gas leaks, localized overheating and electrolysis are just a few of the issues that can affect or destroy the coolant and its inhibitors. Only regular coolant testing and analysis can identify them and the extent of any damage to the system.

Engines, transmissions, and hydraulics are often maintained and repaired without consideration as to how they are affected by the cooling system, which allows the same failures to happen again and again, either to the same piece of equipment or across an entire fleet.

Conducting regularly scheduled oil and coolant analysis together will dramatically improve machine performance, reduce repair and replacement costs, and extend equipment life and reliability.

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