Best Cooling System Additives of 2025

"I have a 2000 Pontiac Grand AM GT with a coolant leak. After trying K-Seal, I was amazed! The engine ran smoothly and I haven't had any leaks for 7 months and 6K miles. It saved my car!"

"I had a 2008 Saturn Vue with a leaky water pump seal. Instead of spending $850, I decided to give K-Seal a shot for $13. It worked instantly, and I've driven it for 2500 miles without issues!"

"I had a very slight coolant leak in my V6 engine. After using K-Seal, the leak disappeared within 48 hours. It's been two years now without any problems, and I saved a lot of money!"

"I found that it works great to help lower the temperature on my Yong Heng PCP Air Compressor. After mixing it with the right amount of water, I noticed a 10°F reduction in temperature, even after driving for two hours on mountain roads!"

"After using this product, my 1984 Suburban now stays below 200°F, even in traffic during the hot summer months. I replaced the thermostat and used this Waterwetter, and it seems to be working well."

"I've been using this product for years in all my vehicles. It's an awesome product that offers great value and helps maintain cooler running temperatures!"

"I found this product works great and significantly lowered the water temperature while towing trailers in the mountains. The test strips really helped me get the right mixture."

"I've been using this Motorcraft product for years to keep my cooling system in good shape, especially for towing in Texas. It's highly recommended by me!"

"I bought this to add to my Ford tractor's coolant to prevent cavitation. The price was reasonable, the mix ratio instructions were clear, and it arrived without any issues."

"I crushed a third of the recommended amount into a powder and poured it into my radiator. After an hour of driving, it helped significantly. I added more the next day, and my heater core has stopped leaking! These GM tablets are a great choice; they prevent sludge in cooling systems if used correctly."

"After rebuilding the engine in my Jeep Wrangler, I noticed a faint coolant smell but no drips. I remembered I had some tablets left from my Tahoe build, so I added two tablets based on my system's capacity. After a good drive, the coolant smell disappeared! Just remember, these are a one-time use product unless you replace components along with the coolant."

"I got these pellets to temporarily fix the cooling system in my 98 Chevy K1500 until I can do a head gasket job. So far, so good!"

"I used this product on my C6 Corvette, and it made the inside look like new. After 18 months, when I changed the radiator, it was as clean as a new radiator inside. The engine block was also very clean, and the engine builder commented on it. This product shows effective R&D for a better environment. Highly recommended!"

"I applied this to my 2000 Tacoma after noticing rust and sediments when changing the thermostat. I used another product first, but it only removed some dirt. Once I used Liqui Moly, it effectively pulled out all the residues. It’s truly a great product!"

"After my car's radiator failed and I had added a stop leak, I used Liqui Moly 2051 Radiator Cleaner. I had replaced most of the cooling system parts, so I can't say for sure how effective it was, but after several weeks, the antifreeze still looked as clean as when added. I would definitely use it again if needed."

"I used Liqui Moly on my 2011 BMW E90 SULEV radiator, which had a very small leak. I was hesitant since I usually avoid additives, but I trusted Liqui Moly due to my past positive experiences. After using it, the leak has ceased, and my car is running top-notch!"

"I bought a 94 Plymouth Voyager that developed a heater core leak. Instead of tearing apart the dashboard, I decided to use Liqui Moly. To my surprise, within minutes of driving after adding it, the leak stopped! I'm thrilled it worked, and hopefully, it will last long enough until I pass it on to someone else!"

"I always keep a can of Liqui Moly on hand. It has sealed a hairline crack in my radiator and lasted for two years! Recently, I found a major leak due to a broken radiator. Even though the product couldn't prevent that, it still performed well without clogging the system. I'm confident in its reliability and will keep using it!"

"I started experiencing PO 420 errors while losing coolant on a mountain pass. After adding the Subaru Coolant Conditioner, the leak completely disappeared. I suspect my head gaskets were leaking, which may have contaminated the catalytic converter, causing the error. Everything is functioning great now!"

"I was unsure about this product when I bought it for $7 during a coolant flush. It seems to be intended for sealing small leaks, although I’m not certain if newer Subarus really need it."

"My 2009 Subaru Forester had a slow leak from the driver's side head gasket. After using this conditioner per the instructions, the leak stopped completely. It's saved me from a costly repair!"

"I had an external head gasket leak and decided to try K-Seal. Every garage suggested either a new engine or a $4000 repair, but this product worked wonders! It's only been a few days, and my engine is dry with the coolant level unchanged. K-Seal saved me a lot of money, and I understand why they offer a money-back guarantee. I highly recommend it for anyone facing a head gasket issue!"

"I found that K-Seal did wonders for my worsening coolant leak on my ‘99 XJ8 VDP. My mechanic couldn’t identify the leak after three attempts. I initially tried K Seal with minimal results, but switching to K Seal Ultimate was a miracle! I haven’t added coolant in weeks, and my low coolant alert has vanished since using this product."

"I’ve had small cracks in my radiators for a while, and K-Seal has been a lifesaver! I saved hundreds on repairs, especially when I discovered two 8-inch hairline cracks in my Cadillac’s block. Using two bottles of K-Seal completely stopped the leaks, saving me an estimated $20,000! I can’t recommend this product enough!"

"I used two bottles in my Cummins 400HP diesel and it lowered the temp in the radiator, preventing overheating in the mountains. In my 2006 40 foot Allegro Bus RV, the results were excellent."

"Every summer, I add one bottle of this Coolant Additive to both my SUVs. It helps keep the engine slightly cooler, so the AC doesn't work as hard. It's easy to use: just pop the radiator cap when the engine is cool and pour it into the reservoir tank."

"I was hoping this would solve my problem, but my Pontiac 455 still ran at 210 degrees at idle, even after replacing the radiator, water pump, and distributor. I tried various solutions, but this didn't completely help."

"I used this product to clean a cooling system in my Mustang that hadn't run for seven years. It left everything looking as good as new!"

"I definitely recommend this product; it worked wonders for me!"