If you’ve ever stood in front of a shelf of coolants scratching your head, you’re not alone. One’s green, another’s red, the label says “premix” and the bloke at the parts counter says “concentrate”. Which is right for your truck, and does colour even matter?
At Fleetguard, we hear these questions every week from workshops across Australia. So let’s break it down.
Premix vs concentrate – What’s the difference?
• Premix is ready to use straight from the package. It is a coolant concentrate already blended with de-ionised water at the correct ratio. Quick, convenient, and safe for topping up in the workshop or roadside.
• Concentrate is highly concentrated coolant that must be mixed with good-quality water (ideally de-ionised or distilled). The ratio matters: too much water and you lose corrosion and freeze protection; too much concentrate and heat transfer suffers.
The choice often comes down to how much control you want. Premix is simple and removes the possibility of over-dilution and contamination when topping up. Concentrate gives flexibility if you need bulk volumes or operate in extreme conditions where ratios can be fine-tuned.
Colour vs performance – Don’t be fooled
One of the biggest myths in the trade is that coolant colour tells you everything. Green, red, blue, yellow – the truth is, colour is just a dye. What matters is the additive technology inside: OAT, HOAT, or hybrid chemistry designed to protect metals like aluminium, copper, and cast iron. Mixing different chemistries can cancel out protection and shorten coolant life.
The risks of mixing coolants
It’s tempting to top up with “whatever’s on hand,” but mixing the wrong coolants can create sludge, clog radiators, and eat away at water pumps and liners. It’s a small mistake that can cost a fleet big money.
Fleetguard’s hybrid coolant, PGPlus, is available as premix and concentrate, while our OAT coolant, PG Platinum, is available as a premix only. Fleetguard heavy duty coolant is approved by Cummins engineering standards.
Whether you need the convenience of premix or the flexibility of concentrate, you can trust Fleetguard to take the guesswork out of coolant selection – so your trucks stay on the road, not on the hoist.
Run cleaner, longer with Filtration Science. Visit fleetguard.com for more information.