This writer was recently invited by the manager of a large independent workshop to investigate an odd vibration on a late-model Dodge Charger when his attention was drawn to a discussion on the colour of engine coolants between two apprentices in the adjacent service bay. The appendices were engaged in servicing a 2014-ish Toyota Camry, and the colour of the engine coolant appeared to fascinate them to no small degree. We can skip over most of the details of what was said, surmised, guessed at, or plucked out of the air, but the gist of it, and later the consensus, was that all engine coolants are the same because they all do the same thing- it's just that the colours were different for marketing reasons.
This writer is not in the habit of interfering in other people’s discussions, so he did not correct the apprentices’ misconceptions about engine coolant formulations, but the discussion did remind him that he had often seen even experienced technicians and mechanics mixing different coolant formulations without regard to the possible consequences of recklessly mixing engine coolant formulations. However, limited space precludes a comprehensive discussion on all coolant formulations here, but since the two apprentices were servicing a Toyota product, we will focus on discussing the pink engine coolant Toyota specifies for use in their vehicles. Let us start by answering this question-
The short answer is that Toyota’s coolant could have been any colour, but when Toyota replaced their LLC coolant (Long-Life Coolant) that was red, with their newly formulated SLLC (Super Long Life Coolant) in 2004, pink was the only available colour. All the other car manufacturers already claimed clear, green, yellow, amber, orange, and even brown for their coolants, so Toyota settled on dyeing their new coolant pink.
The long (and more serious) answer is that before about 2000, the colour of any given engine coolant formulation was entirely due to the additives used in coolant formulations, but this is no longer true for modern engine coolant formulations. Here is why-
Starting in about 2000/2001, all major car manufacturers embarked on extensive engine development programs to improve the efficiency of their engines to meet increasingly stringent exhaust emissions regulations. Since improved efficiencies involved ever-increasing compression ratios and higher combustion temperatures, car manufacturers also began developing more efficient engine coolant formulations at this time to improve the management of engine temperatures.
The upshot of these kinds of research and development programs was that car makers began to specify the use of coolants that were designed specifically to-
While all car manufacturers faced largely the same problems, all manufacturers solved the problems in different ways because the different alloys used in modern engines and cooling systems placed different demands on engine coolant formulations. We need not delve into problems involved in creating efficient circulation patterns in modern engines here, but suffice it to say that Toyota elected to dye their newly created SLLC formulation a vibrant pink colour to ensure that we always use the correct coolant to ensure the efficient thermal management of modern Toyota engines between the long coolant replacement intervals that now average about 150 000 km.
It is worth noting that although the old-style red LLC is still available to accommodate pre-2004 Toyota engines, this formulation will not provide the level of protection that modern Toyota cooling system components like electric water pumps, EGR coolers, and heat exchangers on late-model Prius and other hybrids require.
As a practical matter, mixing different coolant formulations in a modern Toyota engine can have serious and expensive consequences; consider the statement below that was taken from an official Toyota publication-
"...[in order] to avoid technical problems, only use "Toyota Super Long Life Coolant" or similar high-quality ethylene glycol based non-silicate, non-amine, non-nitrite, and non-borate coolant with long-life hybrid organic acid technology. Follow the manufacturer's dilution recommendations on the label. (Source: Toyota USA)
Just like engine oil formulations, coolant formulations also contain additives and constituents that are not always compatible or miscible with the additives in other formulations. In practice, such incompatibilities could produce one or more of the following effects-
So from a reliability perspective, it is crucially important to use the engine coolant specified when servicing a modern Toyota engine. However, it is equally important to understand that hybrids and electric vehicles often require the use of highly specialized coolants in their various cooling systems.
NOTE: If you were not aware, hybrid vehicles can have as many as five or six separate cooling systems to keep various parts of the high-voltage system cool. These systems typically use coolants with characteristics and chemical properties that are different from those of "normal" engine coolants, and since most of these specialised coolant formulations are also often dyed pink, be sure to consult all relevant service information before draining any cooling system on any modern Toyota vehicle, which brings us to-
Image source: AI-generated image/Shutterstock
The primary difference between Toyota’s red and pink coolants involves the principal ingredients in each formulation- consider the “recipes” below-
Pink Super Long Life Coolant
Red Long Life Coolant
Each formulation contains other ingredients besides the ones listed here, but it should be obvious from the listed ingredients that the two formulations differ in meaningful ways. Sadly, one needs to be a chemical engineer to fully understand what it is that each ingredient does, but the point is that each formulation is designed to provide the maximum amount of protection against corrosion and overheating- provided that each formulation is used in engines that were designed to benefit from each formulation.
For instance, while red coolant can be diluted by as much as 50 per cent with distilled water and still work as expected, pink coolant should never be mixed, even with distilled water because it is already diluted to a specified ratio. Therefore, diluting pink coolant further reduces, or can even destroy the coolant’s ability to protect the engine against corrosion and overheating.
However, since some of the water in pink coolant evaporates over time, the cooling system can be temporarily topped up with distilled water. Note, though, that the recommended coolant replacement interval should never be exceeded or ignored, because although Toyota’s pink engine coolant is a marvel of chemical engineering, some critical additives do become depleted over time, and the overall formulation eventually loses its effectiveness, which leaves us with-
In Part 2 of this article, we will ponder the question of what constitutes a coolant leak, and look at some components in modern Toyota engine cooling systems that require the exclusive use of Toyota’s pink Super Long Life Coolant.
