help with coolant math...

[MRYGearHead]

Hi,

I need help with some coolant math, for switching from 50% to 60% antifreeze...

What I want to do is remove x gallons of coolant, then replace it with 100% Zerex Asian antifreeze (Honda no longer sells 100% undiluted, full strength antifreeze, this antifreeze is 100% compatible)...

I have approx 2.3 galleons capacity (rad, engine and recovery tank, etc).

Currently, I have 2.5-3 year old (40k miles) Type-2 Honda coolant (replaced during a full timing belt service). I'd like to just remove what's needed, to switch to 60% antifreeze. Last year, overnight, it got down to, -20F-something, and never got above negative 10F. I've read somewhere that the -34F rating is for storage/ none use temperatures, not recommend for use.

The problem is the AI math and my math doesn't match at all...

 

[georgef]

We need to know the capacity of the system before we can do the math.

 

[altaylar]

So you are essentially mixing 2 liquids, one is 50% antifreee, the other is 100% antifree, and you want to reach 60%.

The math will be as follows
(V_1*50% + V_2*100%) / (V_1 + V_2 ) = 60%

V_2 is the amount of pure antifreeze you need to add. V_1 + V_2 is the amount of coolant your system holds, and V_1 is the amount left once you remove V_2.

In a nuthsell, you want to replace 20% of your coolant mix with pure coolant

 

[daniel327]

you want to replace 20% of your coolant mix with pure coolant

^^^ This. Remove 20% of whatever is currently in the cooling system. Re-fill cooling system with 100% Zerex coolant.

 

[MRYGearHead]

We need to know the capacity of the system before we can do the math.

Doh. I fixed that above. Its 2.3 Gallons.

 

[MRYGearHead]

Hears my math:
I have currently 50%. I want 60%.
2.3G. 10% is 0.23G. Or approx a 1/4 gallon.

 

[ecotourist]

Why do you want 60% antifreeze?

50% antifreeze can handle -20F without any problem. In fact it should be good down to about -34F. Prairie people typically use a 50% mix and -20F is a pretty ordinary winter day. I only ever had a radiator freeze once and it was very cold that day (more like -35F, maybe colder).

It used to be said that 50% antifreeze was better than higher concentrations for cooling too.

The trick is getting to an actual 50% concentration. If you're just draining and filling it's easy, just drain and fill with a 50% solution. But if you're going to flush the system with water you really need to use concentrate and distilled water.

 

[altaylar]

Hears my math:
I have currently 50%. I want 60%.
2.3G. 10% is 0.23G. Or approx a 1/4 gallon.

you want to double that

 

[doitmyself]

And if you are stickler for details, don't trust the 2.3 gallon approximate capacity. I have seen huge variations from the stated manual capacities. Get yourself a coolant refractometer.

 

[MRYGearHead]

And if you are stickler for details, don't trust the 2.3 gallon approximate capacity. I have seen huge variations from the stated manual capacities. Get yourself a coolant refractometer.

I have the cheap prestone type.

 

[MRYGearHead]

Why do you want 60% antifreeze?

50% antifreeze can handle -20F without any problem. In fact it should be good down to about -34F. Prairie people typically use a 50% mix and -20F is a pretty ordinary winter day. I only ever had a radiator freeze once and it was very cold that day (more like -35F, maybe colder).

It used to be said that 50% antifreeze was better than higher concentrations for cooling too.

The trick is getting to an actual 50% concentration. If you're just draining and filling it's easy, just drain and fill with a 50% solution. But if you're going to flush the system with water you really need to use concentrate and distilled water.

Regarding, getting actual 50%:
This is why I'm rounding up...

 

[MRYGearHead]

The 2.27 (2.3) Gallons is a dry fill.

Cooling system backstory:
I've done 3 drain and fills (one was) fully, since I've owned the car. I bought it, back in 2019 (its a 2012 car). The fist one I did many times, because an unknown green coolant was added to the coolant, when I bought it. I used distilled water and quite a process to clean the old coolant out and replace it with type-2.
I did a common drain and fill, once (one year) after that. Then it got done again, during the timing belt service, 2-3 years ago. In other words, too many times compared to most normal people.

 

[ecotourist]

Re actual 50%:
This is why I'm rounding up...

What do you mean?

If you have 50% and drain some out and add 50%, it's still 50%.

If you're draining and flushing with water, you flush however many times you want, drain one last time, then add 100% coolant equal to half the cooling system capacity and top up with water, ideally distilled water.

 

[MRYGearHead]

What do you mean?

If you have 50% and drain some out and add 50%, it's still 50%.

If you're draining and flushing with water, you flush however many times you want, drain one last time, then add 100% coolant equal to half the cooling system capacity and top up with water, ideally distilled water.

I was commenting on you last sentence, few posts ago (post #7)...

Regarding this above comment of yours (Post #13), about, flushing with water comment. I only did that, when I bought the car, back in 2019 - Please read my above, "cooling system backstory" (see post #12)...

 

[Hirev]

Get you a antifreeze coolant refractometer for automobile antifreeze this is the most accurate way. Everthing else is just a good guess. You adjust your coolant percent to freeze point. A 50/50% is -34 deg F.......60% coolant 40% water is -62 F on the refractometer.

 

[samven]

This is what you need, I bought this 5 years ago and it has been great but there are others I am sure come from the same factory. Start with 1/2 gallon drive and test. https://www.amazon.com/dp/B07TMMSX15

 

[HemiBenny]

I think you're overthinking this a little bit.

Last year, it got down to -20F overnight and never went above -10F? How many times? How long did it stay that cold?

If it's within the service interval and the mix is 50/50, leave it until it's time to service it again. Then, do a 50/50 mix again, it’ll be fine.

 

[Capt W]

Before doing all the guesswork, have you pulled the block drain plug(s) for a thorough drain? I don't know why so many people don't want to do this. After I flush my cooling systems, I pull the plugs and get a thorough drain. Mixing the desired concentration and refilling is then a snap.

BTW, where are you taking/storing the vehicle? You're not getting temps like that in Monterey.

 

[MRYGearHead]

I'm not in Monterey any more. I retired. I'm in northern mid Missouri now. I guess, I waited too long. This week its not expected above freezing. But luckily I doubt it will get cold as it did last year. I might over thinking it. Most people just dont change there coolant at all.

Regarding draining the block. If the drain plug brakes, its unreparable. Mines in a difficult place to access. My coolant was changed in less than 3 years ago. I dont plan on doing that kind of change. But I'll look at the drain plug location and I'll rethink it. I will do in a full drain and fill when I reach 60k miles in year. As often as I do this, I dont think I really need to get it 100% out of the engine.