Testing Red Line’s New SuperCool Coolant & CSF’s Tundra Radiator

Red Line has released a new high performance coolant that has its famous, and universally used in motorsports, Water Wetter surfactant additive pre blended in.  Red Line Supercool comes in two variants, one that is 50/50 pre blended and ready to use, and a concentrated version where you can control the ratio of coolant to water.  This is useful in very cold climates or for cars that are stored where you might want a higher concentration of coolant to water.

Red Line Supercool fortified with Water Wetter is designed to maximize the performance of the cooling system with superior protection against cavitation and corrosion/erosion. Using the pre mixed SuperCool protects the entire cooling system. Keeping new components like new for 5 years/150,000 miles and prevents further damage to older components. Red Line’s proprietary Water Wetter coolant additive formula enhances the fluid’s ability to transfer heat.  Red Line says its coolant can reduce operating temperatures by up to 20 ̊F and prolong the life of the entire cooling system.

Just how well does it work? Well, we decided to put it to the test.  We chose a late model Toyota Tundra to do our testing, because we figured that a heavy duty vehicle like a Tundra would need to have good cooling for doing stuff like towing and hauling a lot of weight. Our test subject was a 2018 Toyota Tundra with a 5.7 liter V8 and 50,000 miles on the odometer. We will also be using this opportunity to test CSF’s high performance aluminum radiator for the Tundra.

Before we get into the results, let’s go over our testing procedures. We will be covering a number of tests in this article:

  • OE coolant with OE radiator (cooling system baseline)
  • Redline Supercool with OE radiator
  • Redline Supercool with CSF aluminum radiator

Thermocouples were added to the coolant hoses going into and coming out of the radiator. This data along with ambient temperatures were logged with our trusty Omega RDXL4SD temperature datalogger. We controlled the ambient air temperature to within a few degrees during the entire test by opening and closing the dyno room doors, this was very effective. The dyno fan speed and position were kept constant during all tests.

We obtained a new set of Genuine Toyota radiator hoses and a couple of temperature sensor adaptors to tap into the coolant flow. One for the radiator inlet and one for the outlet.  We used Omega K-type thermocouples.

Here’s a closer look at our radiator hose adaptors with thermocouples installed. The thermocouples are inserted so it they are about half way into the adaptors.


  1. Great scientific method use to show relatable results and data. I’m sure any 13yr old truck would benefit from a nice new CSF radiator. Would love to see this type of analysis put to the test on something like the turbocharged F-150s with electric only fans and such.

    Mike, are you planning on looking into the finally redesigned 2022 Tundra with the turbocharged v6?

    1. The better test would probably be something that is more marginal on cooling. A Tundra is super overcooled.

      1. I meant as a way to see if the Tundra it overcooled even in the world of vehicles rated to tow 10klbs or if all modern half ton trucks have this kind of cooling capability. A turbocharged engine under load in the heat with two electric fans sounds like a different ballgame compared to a big n/a v8 with a huge mechanical fan.

  2. so 20 degrees cooler sounds amazing and all, and honestly I can really use the extra cooling capacity, but I’m nervous about anything with water wetter (and similar products) in it. Just google water wetter sludge and you’ll a bunch of results. I’m particularly concerned about it cause it happened in my car with the previous owner (friend of mine, I saw the sludge myself). It happened after just 1 track day… and there wasn’t an improvement in cooling.

    On the other hand I know it works for a lot of people and they don’t get the brown sludge after just 1 track day. Is there a trick to using water wetter? Something specific that needs to be done to prevent the sludge?

    If it matters, the car in question is a turbo NC Miata with the 2.5 Duratec swap. At the time of the sludge incident it was still on the original 2.0 and was supercharged.

    1. I know the concentration use for water wetter is very low. I think it’s something along the lines of 1 cap full per quart or gallon if I recall. I’ve only used it in motorcycles where glycol based coolant isn’t allowed on the race track. I’ve had great success with it for about 15 years now. I flush it annually.

    2. I have never experienced brown sludge in anything with water wetter which is scores of cars and everything I have run on the track ever! In my case I run water wetter with just water. Brown sludge could be the water pump lubricant in coolant coming out of solution. Or it could be combustion residue from a blown head gasket not related to the water wetter.

      1. @Rob Is too much water wetter something that causes the brown sludge? I can’t say for a fact he followed directions, but he’s the type of guy to follow directions

        @Mike I know it works for a lot of people, but it also ends in brown sludge for a lot of people. Googling it brings up tons of results so its not a one off thing…
        as far as the brown sludge being caused by something else, thats definitely not the case here. There was no sludge before, he drained in and put in fresh coolant/distilled water at a 25/75 mix plus water wetter, did a track day, got the sludge, drained and flushed a couple times to get all the sludge out, and went back to a 30/70 mix with no water wetter and the sludge never came back. This happened when the car was about a year old had under 5k miles on it, so its not an old car thing.

        could high temps cause this? the car did get to the low 240’s water temp on the track before backing off. This is with and without water wetter, so its not something else in the engine that was caused by hitting those temps

        1. I feel like the mixture gets too saturated, especially at higher coolant concentrations and something falls out of solution. I doubt it’s harmful.

          1. is 25-30% considered a higher coolant concentration? thats pretty low in my book… maybe you read the numbers I wrote flipped around? the 25-35% is the coolant and the water is the rest.

          2. ok, I thought it was 75% coolant and 25% water, nevermind! Perhaps it’s oxide residue that the water wetter strips off the inside of older radiators? It would be interesting to see if it reoccurs.

          3. But it was a new radiator… oem stuff had less than 5k on it and a new Koyo went in just a couple track days before…

            I may try this Redline coolant if I ever get around to finishing this car depending on how it handles temps with regular coolant (25% mix). going off general NC experience it’ll need all the help it can get… It now has another new radiator in it, a CSF triple pass. But the engine is a bit of a mystery 2.5, not really sure which car it came out of and with how many miles…

  3. What kind of coolant pressure is the maximum with a CSF radiator? It seems like you could substantially increase the pressure without plastic endtanks.

    1. I would not run more than 25 psi and to do that you have to use good hoses and high quality clamps everywhere, even those little dinky ones you don’t realize you have like in your heater core under your dash and that small throttle body hose buried under your manifold.

      1. does running higher pressure actually help with cooling, as in reducing temps? for example if all else was lab test equal, would the higher pressure system run any cooler? or is it just more headroom before you need to start worrying about blowing a headgasket or whatever due to the higher boiling point?

          1. They run 30-40psi in F1, although they have hard pipes and obviously don’t run band clamps.

            “ Whilst we use the term water, the actual fluid is a water/glycol mix. This is kept under pressure at over 2.5bar to raise the boiling point, so that the engine can be run hotter at +120c in order to reduce the size of radiators required.”

            25 psi is a substantial improvement, but you’re right, there are a lot of weak links. I imagine you would want to upgrade your clamps and change your hoses to silicone, and obviously only do it for a track car.


    2. Interesting stuff on the coolant temps F1 cars runs. Makes sense on a couple fronts. Gotta run the higher pressures to prevent boiling. High coolant temps increases delta temp to ambient, so smaller radiators and less aero drag. Higher coolant operating temps, less heat loss from combustion to the coolant, so improved thermal efficiency. Well, F1 is over 50% brake thermal efficiency now, super impressive.

  4. Many comments:

    Water Wetter does have a rep for sludging. If you call Redline they will acknowledge same. They have a newer variant they can recommend that is actually for diesel use. Might be what was used here.

    That said I support and use surfactants. I happen to prefer Rislone’s Hyper-Cool, which is really Hyper-lube’s product, but now I can buy it at Walmart.

    The test results, while not invalid per say, aren’t really indicative enough. A surfactant increases the thermal transfer rate of water. You may see this as a reduction in coolant temperature, but measuring same is a poor indicator.

    Why? Because the job is to increase the removal of heat from the engine block and more efficiently transfer it to the water. The water temperature in the engine remains controlled by the thermostat.

    Now since thermal transfer increases at the radiator too, if one looks at coolant temperature exiting the radiator it will have dropped as a result of the radiator efficiency increase. All well and good, and that part of the test is valid.

    If you get a different temperature leaving the engine your test is bad, the thermostat won’t allow that. Ergo that part of the test is not only flawed, (if it captured any data), it captured the wrong data too.

    There are only two test points that matter: Coolant temperature at the radiator exit, and cylinder head block temperature. If you see a lower (and you will) value at rad exit you’ve confirmed increased thermal transfer at the radiator. If you see a lower CHT temperature (of the head, not the water), you’ve confirmed you are transferring more heat from the head into the water. This “should” bring the thermostat open more and water flow will increase to match. Water temperature exiting the block should remain unchanged!! but block temperature will go down, as should oil temperature.

    In turn one can run more timing or less octane as a lower CHT results in less knock. Either will increase power

    Yes, higher pressure increases cooling efficiency. The boiling point of water goes up, and this allows a higher coolant temperature. The greater the difference between coolant media (lets say water) and the ambient temperature (lets say of air) the greater the thermal transfer rate. However, that’s all headroom. And while that’s true of radiator efficiency it reduces thermal transfer rate in the engine, so…

    Nor does it matter unless you exceed the boiling point of water+coolant. Thus in practice it has little value to anything we’re doing. F1? I guess so.

    To increase cooling one must do one of a few things:

    1) Lower the thermostat opening point (always).
    2) increase the thermal capacity of the coolant. A surfactant, or a higher mix of water to anti-freeze.

    Then, if the engines creates more BTU than can be shed one must then (do some of):
    1) Increase water pump flow.
    2) Increase air flow.
    3) Increase radiator area (size first, then depth if that’s all that’s left).
    4) Again increase the water to anti-freeze ratio (never go below 30%).
    5) Introduce additional cooling. I’d suggest an oil cooler.

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