Anyone who's ever had the misfortune to drive a stock Triumph Stag will be aware of the importance of engine coolant. Made up of a mixture of water and antifreeze, coolant is integral to the smooth running of your car. It lowers the freezing temperature of the water to keep it flowing through your engine in low temperatures and also raises the boiling point to keep it running clearly in the summer heat. Modern coolants also include corrosion inhibitors which will keep your engine's insides healthy.
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Coolant also needs regular checking to make sure it's still effective and won't cause any damage to your engine. In winter, if your antifreeze isn't effective it can freeze, something that can cause serious damage to your engine internals. While in summer, overheating will become a common occurrence, worrying news for seals, head gaskets and cylinder heads.
All of that damage sounds expensive which makes a small antifreeze tester a brilliant investment. These tools are simple to use, take up next to no room and could potentially save you a boat-load of cash if you catch your antifreeze acting up before it has the chance to do serious damage.
The best antifreeze testers
Sealey AK4122 Disc Type Propylene Glycol Antifreeze Tester
The best quality antifreeze tester
A very simple but effective antifreeze tester from Sealey, this tool makes use of floating discs to test the quality of your antifreeze. It works like a pipette that you squeeze and then release to pull coolant into the chamber. Then you'll need to wait a couple of minutes to see how many of the discs rise. The more that rise, the healthier your coolant. There are no instructions provided so it's a good idea to watch a video demonstration if you're new to antifreeze testing.
Unitec 74275 Coolant Testing Device
The best antifreeze tester for beginners
The easiest antifreeze tester to read we've come across, this handheld device from Unitec comes with a clear display for showing the health of your coolant. It's also well-made and designed not to drip coolant over your engine as you're working on it thanks to the hydrostatic fluid lock. If you're after a simple antifreeze tester, this is the best option.
The best antifreeze tester for budding amateur mechanics
The fanciest option here isn't just a device for testing antifreeze, it can also be used to test AdBlue, battery acid and windscreen washer fluid. Use the supplied pipette to collect a sample and place it on the plate like a real scientist. You then need to look for the eyepiece to see the conditions of the sample. It's a clever option if you like working on cars yourself, even if most people aren't regularly testing their battery acid that much.
Gunson 77105 Antifreeze Coolant Tester
The best budget antifreeze tester
Working similar to the Sealey antifreeze, this option sucks coolant into a testing chamber similar to a pipette. However, unlike the Sealey, this makes use of a dial (reading in both degrees Celsius and Fahrenheit) to test how good the antifreeze is. Some reviews have questioned the quality of this tool, but it is the best value option here and has a plethora of solid reviews to back it up.