I really haven't done a comparison. Just used whatever happened to be around at the time.

Perhaps we'll get some good feed back here from others.

Would a Pilsner be better? It's light in color, so I suspect it would dissipate heat better than Bock?

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Recently, the radiator/coolant icon on the dash of my 1986, 560SL lights up intermittently. However, the guage does not indicate that the car is running hot. I noticed that the coolant in the overflow reservoir is about an inch below the point where the reservoir is molded together. Could this be causing the icon on the dash to come on?

Steve M
1986 560SL
90K

The "low coolant" light is triggered whenever the coolant level in the reservoir is considered low and needs to be topped off. Not an overheat issue as there is still plenty of coolant available to circulate through the engine. It just gives you fair warning to address the issue before you run out completely and cause real permanent damage.

If you top off with coolant/tap water/distilled water/Kool Aid, etc. whatever, the light should no longer be illuminated. If it is still illuminated, then the corrosion on the coolant sensor terminals are causing a "false positive", in which case you need to replace the sensor (located near the bottom of the coolant reservoir).

Back on topic:

My indie say "distilled water only!" but from experience, I find that the issue is really about regular maintenance, not chemicals. Although there are recommended coolant products for MB, the issue about water really is about the duration of said mixture circulating through the engine before it is refreshed.

Same with the "dino vs. synth" argument. If you are changing oil at regular intervals (7500 mi), it should not matter what oil you are using.

For either case, it you are going along with no regard for routine maintenance using the same recirculated oil and coolant, there is no doubt you are going to destroy something eventually, regardless of the "snake oil" properties of the product(s) being used...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

We buy premixed coolant by the semi-trailer load for industrial engines: it's glycol and deionized water, mostly because at some locations the water is of poor quality, full of iron, etc., but also because we can be certain the corrosion inhibitors are there and the freeze point is correct for the location. We use enough glycol to get appropriate freeze protection, but no more, as the cooling capacity of the systems is reduced as the glycol concentration increases (but the boiling point in a pressurized system increases, I know; these aren't pressurized as cars' are).
I opened my Benz up after 20+ years of somewhat indifferent care by the PO and found... nothing wrong in the cooling system. It had probably had the same green stuff in it for 5 or more years. Our tap water is fairly soft and doesn't cause problems. I have a car I've owned since 1974 and no problems ever with the cooling system, with just general good maintenance, nothing elaborate. If your tap water does not ruin the coffee maker, sinks, toilets, or water heater, you probably won't have any problem with it as long as you use the right coolant and change it every so often; if it does, don't use it in your cooling system.
Don't spend all your time worrying about your car; spend most of your time enjoying it.

My 300TE has some corrosion in the system from the use of tap water instead of distilled water.

Distilled + Correct Antifreeze = perfect

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Aluminum heads on iron blocks create enough problems without introducing more by using impurities into the cooling system. If your car is getting up towards 20 years old I would be using every trick in the book to ensure trouble free motoring.

Use the approved coolant. Cheap insurance. By some extra for topping up. ( The Lord only knows what all those added chemicals in the water supply are doing to our human bodies over a lifetime)

In another life I worked in the Asian tropics. Our company installed huge backup power supplies and batteries for our projects. These batteries had a life of 15 years. Injudicious maintenance could shorten the life of these by half. We are talking about battery packs that are larger than a standard W140 S class and costing big bucks.

The air was so polluted in SE Asia by industry and vehicles but more importantly by the hundreds of active volcano's venting sulfuric acid etc etc, that even local spring water first distilled was not pure enough to top up our batteries. Our purified water came from Norway.

thanks to everyone for the informative replies. I've since added the distilled water to top of the reservoir, but have not had an opportunity to see if that keeps the dash light from illuminating. Update will follow.

also, I'm new to this site, and VERY impressed with the active response by members. Thanks again.

Steve M.
1986 560SL, 90K

FWIW i only used distilled water in the very large windscreen washer bottle mixed with barrs bug and tar remover. i never get blocked wiper nozzles and windscreen is not gritty