Philes’ Forum – Summer 2018


By Vic Lucariello, Sr.

Hello bimmerphiles! This time out I would like to talk a bit about that often neglected fluid inside your Bimmer’s radiator and engine: the coolant.

When I got my first gas-station job, uh, some years ago, so-called “permanent” coolant [AKA: antifreeze] was a relatively new thing, and the old non-permanent coolant was still available. At the time, “permanent” coolant denoted a coolant that could be left in service year-round. It did not denote a “lifetime” coolant or “long-life” coolant. One brand’s non-permanent stuff was Zerone while their new-fangled permanent stuff was Zerex, which is still available today from Ashland Oil [Valvoline].

In addition to providing freeze protection, coolant must also provide corrosion protection. Most permanent coolant is based on ethylene glycol, which provides great freeze protection – [-34 F] when mixed 50/50 with water – but little or no corrosion protection. The corrosion protection is provided by the additives in the base ethylene glycol stock.

Prior to the advent of permanent coolant, each Fall one would have to drain the cooling system of its water [with “rust inhibitor” added for corrosion protection], and fill the system with Zerone, or the equivalent in another brand. Then in the Spring, the Zerone would be drained, the system flushed, and water/rust inhibitor reinstalled for the warm weather. [If the non-permanent coolant was left in for the warm weather, it would boil out of the non-pressurized cooling systems of the day.] This was one of the first auto-repair jobs I did with my Dad on our 1951 Chevy, as prescribed in the owner manual, which I still have.

Dad taught me that, in addition to draining the radiator, we needed to remove the drain plug on the block as well. He also taught me that the pipe-thread drain plug could be replaced with a petcock so that future drains would be easier. Every car I have ever owned that had pipe-thread block-drain plugs received this modification. Thanks, Dad.

In those days, and for decades afterwards, there was really only one type of permanent coolant, and it could be used in virtually any car or truck. I recall pallets of it being delivered to the gas station each Fall. Even though the permanent coolant did not need to be replaced annually or semi-annually, we did so for quite a few years. In today’s auto-repair-industry patois, this would be called “wallet flushing”. In defense of that decades-ago practice, the owner manual for Dad’s 1961 Comet, which came equipped with permanent coolant, does prescribe annual coolant changes. The manual also makes the distinction between permanent and non-permanent “antifreeze”, even by 1961. Auto-repair-industry consensus is that, while traditional permanent coolant provides good corrosion protection, its service life is limited to a couple years, after which the corrosion inhibitors have become depleted.

Circa 1996, General Motors introduced its Dex-Cool coolant formulation, which is a long-life, say 5 years, ethylene glycol coolant with a significantly different additive package than traditional permanent coolant. It is also repair-industry consensus that one does NOT want to mix traditional coolant with Dex-Cool. The resulting goo is dubbed by some as “Death-Cool”. This is NOT a fault of GM or Dex-Cool. Rather, it is the fault of ignorant installers, professional or otherwise.

Other vehicle manufacturers adopted their own versions of long-life coolant, each differing significantly, in terms of additives, from Dex- Cool and traditional permanent coolant. [See Photo #1 for what I use in my shop.] The automotive aftermarket followed suit with their own offerings, SOME of which have specific auto-manufacturer approval. Dex-Cool, other long-life ethylene glycol coolants, and traditional permanent coolant fall into about six major types, some of which overlap. It is a source of great confusion among professional auto technicians, and the subject of debate on professional forums such as iATN, the International Automobile Technicians Network.

[Photo #1]

BMW has for years had their proprietary version of long-life coolant, and I have used it for years with success. Several aftermarket coolant manufacturers offer coolants that THEY RECOMMEND for BMWs, but I know of no such manufacturer that advertises that their coolant is APPROVED by BMW. [If you know of any, please advise.] This is a significant distinction that you need to be aware of when choosing coolants and motor oils. “Recommended For” and “Approved by [auto manufacturer]” are not the same.

On the other hand, aftermarket companies such as Ashland Oil/ Valvoline and Pentosin expend significant resources developing coolant-additive packages to satisfy the major coolant types used today. So I don’t think these companies, with inveterate reputations to uphold, would cavalierly recommend coolant for use in a particular vehicle marque. Both companies offer coolants that they recommend for use in BMWs.

Mixing any full-strength ethylene glycol coolant with water in a 50/50 ratio will result in a freeze point of about -34 F. You may say, “Hey, it doesn’t get anywhere near that cold here, so why do I need to use that much coolant?”. The answer is that diluting the coolant with more than 50% water will raise the freeze point, but it will also dilute the additive package, which is designed for a 50% dilution. Diluting the additive package will shorten the life of the coolant. You can buy an inexpensive hydrometer which will tell you the approximate freeze point of your coolant. [See Photo #2.] You really should keep the concentration around 50%, preferably a bit higherthan lower. For the more technical [anal?] among us, a refractometer will tell you the coolant concentration within a few percent.

[Photo #2]

If you have read this far, here are some suggested takeaways regarding coolant:

  • If there is any doubt in your mind whether a particular aftermarket coolant is APPROVED by BMW, use BMW coolant. I do. It may cost a bit more than others, but so did your Bimmer.
  • There is a nationally-known company that offers a single coolant that they claim is suitable for “all makes, all models”. Given the wide variety of coolant formulations available today, I am quite skeptical of this claim.
  • The color of a coolant is not a reliable predictor of its formulation.
  • You DON’T want to mix coolants of differing formulations.
  • Use distilled or deionized water for mixing with coolant.
  • Get yourself an inexpensive coolant hydrometer to check your coolant level.
  • If you have any doubt as to what coolant is in your Bimmer, have the system THOROUGHLY flushed [This takes hours, so be prepared] and refilled with BMW coolant and distilled water.
  • Keep a container of BMW coolant mixed 50/50 with distilled or deionized water for topping-up use.
  • Some coolants are available either concentrated or “pre- mixed”. I recommend that you buy the concentrate and mix your own. You can check your work with your new hydrometer or refractometer.

If you found this column to be interesting, let me know and I will follow up with some coolant-flushing tips.

That’s all for now, bimmerphiles. See you next time.

Anyone wishing to contribute to Philes’ Forum can contact me at I’m interested in comments, tech tips, repair /maintenance questions, repair horror stories, emissionsinspection sagas, product evaluations, etc.

© 2018; V.M. Lucariello, P.E.

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