Piston Slap: A One-Size-Fits-All Coolant?

Sajeev Mehta
by Sajeev Mehta
piston slap a one size fits all coolant

TTAC Commentator ErikStrawn writes:

Over the years I’ve tinkered with a bunch of different cars. Back in the day, you could put green ethylene glycol coolant in every car and it worked fine. If you had a car with the brand new DexCool, it was recommended to drain it and refill with the green stuff. Then some manufacturers went to the red stuff, and VW/Audi went to some other stuff that sludges up if mixed with the green stuff.

A couple years ago I bought an insurance auction VW Beetle TDI, and when I replaced the front end/radiator/etc., I flushed the engine out with water and switched the car to traditional green coolant.

My ’06 Mustang has 140K on it, and living in a constant state of having too many projects, I’ve neglected to change it until now. I’m of a mind to flush it out and run green coolant, but I know aluminum motors aren’t exactly tolerant of the green stuff.

I intend to transition my entire fleet to one coolant. What is a good one-size-fits-all coolant that is readily available? I’m in Oklahoma, and it freezes here, so running straight water is not an answer. Should I stick with the green stuff and replace it more religiously?

The Mustang is bone stock and ultra-reliable, so I don’t want to run coolant that has a propensity to turn acidic and erode the cooling passages. Is the red stuff any better? What is it called and can I find it at a truck stop at 3 a.m.? Does VW’s coolant have any advantage?

Sajeev answers:

Please note that I both know and admire Mr. Strawn from his work building race cars in the 24 Hours of Lemons…the wretchedly wonderful Jaggernaut with the Big Block Cadillac motor notwithstanding.

That said, what you propose will never work these days. Engine coolant is now color coded for good reasons, apparently.

If I googled this correctly, your VW TDI uses G13: a purple colored, Silicate Organic Acid based coolant. The Mustang uses either a fully Organic or Hybrid Organic coolant (orange or yellow). Neither should use the green stuff, that’s just clinging to old technology. Perhaps you can run the VW’s purple stuff in the Mustang, I doubt the opposite is possible without leaks, gasket failures, or expediting a possible plastic water pump impeller failure problem.

Who thought plastic water pump impellers were a good idea?

Not to mention that VW G13 coolant is usually a few bucks more than the yellow/orange stuff. A good color chart with the differences can be found here.

So do yourself a favor and blow out the green stuff, replacing it with the proper purple coolant in the VW.

What say you, Best and Brightest? Can you do a one-size-fits-all coolant?

[Image: Volkswagen Group]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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2 of 39 comments
  • Rrhyne56 Rrhyne56 on Oct 22, 2019

    I'm driving a 2014 Subaru Impreza. Did some coolant research and discovered that in 2008 Subaru switched to Super Coolant, which is a sort of blue color (most guys know eight colors, like the basic Crayola box). I snuck into the service area at the local Subaru house and talked to the mechanics. They basically said to not use anything green, then gave me a gallon of the latest and greatest. Bottom line would seem to be, do your research, do a thorough purge and refill. Oh for the old days of points and condensers, of wheel bearings that have to be packed on the regular (I kid).

  • -Nate -Nate on Oct 25, 2019

    I'm way behind the curve here as I only learned of the blue / purple coolants recently . My current water cooled vehicles use G05 . It's important to _ASK_the counter person at your FLAPS for the undiluted coolant, it never seems to be on display and as mentioned it's an easy way for them to essentially double their profit . In Sunny Southern California the only place I can find distilled water under at least $1.35 is wallymart (plus you get to look and laugh at all the wallymartians) . I keep a few gallons of distilled water in the kitchen at all times . Another good and timely article, do your cooling system service now so you won't be doing it in the snow when you discover your old jalopy (not everyone here has newer vehicles) has more crud in there than you realized . -Nate (who needs to replace a noisy outer wheel bearing A.S.A.P.)

  • Norman Stansfield Why are leaf springs still a thing on this truck?
  • Syke The expected opening comments. Have had mine for two years now, the car has done exactly what I want out of it, and a little better. I'm quite happy with the car, haven't had to adjust my driving style or needs in the slightest, and . . . . oh, did a mention that I don't give a damn what today's price at the pump is?Probably going to go for a second one in the coming year, the wife's happy enough with mine that she's ready and willing to trade in the Nissan Kicks. Eventually, the not often used van will end up getting traded on a Chrysler Pacifica Hybrid, basically ensuring that we don't use gas for anything except the occasional long trip.And the motorcycles.
  • Bobbysirhan I've never found the Allegro appealing before, but a few years of EV rollouts make it seem downright desirable.
  • Scoutdude I know that dealership. Way back when my friend's grandfather was that Turner that owned the Chrysler Plymouth International dealer, in MacPherson. Of course the International was dropped when they didn't deem the Scout reason enough to keep the franchise. I moved from there in late 1978 so it is possible I saw this running around town way back when.
  • Lou_BC "Overpriced" is a misnomer. Arguably, if they are selling they are not overpriced. "Dealer mark-up above MSRP" is a mouthful but more accurate. Simple, don 't buy anything marked up. A computer will help you search the country. It's a PITA but doable.