Can You Use Water as Engine Coolant?
Water is half of the coolant mix, but straight water gives no freeze protection, boil-over resistance or corrosion protection.
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The reservoir is low on a hot afternoon and the only jug in the garage is water, and the question is whether the tap can fill the gap. Can you use water as engine coolant? Water is one half of the mix, but straight water gives the system none of the freeze protection, boil-over resistance or corrosion protection the listings state, so the answer is to use the 50/50 coolant, not water on its own.
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Zerex Dex-Cool Antifreeze Coolant Concentrate 1
A 1-gallon orange concentrate that mixes with clean tap water at 50/50 for freeze protection from -34 to 265F, with a 5 year/150,000 mile guarantee.
Pros
- Mix ratios stated for -34 to 265F at 50/50
- Organic acid technology resists rust, scale and corrosion
- 5 year/150,000 mile guarantee
- Protects all cooling system metals, including aluminum
Cons
- Concentrate: it must be mixed with water before use
- No ready-to-use 50/50 version is stated
- Mixing needs clean tap water or demineralized water
- No shelf-life figure is stated
Zerex G05 Antifreeze Coolant Concentrate 1 Gallon
A 1-gallon yellow concentrate that mixes with clean tap water at 50/50 for freeze protection from -34 to 265F, with a 5 year/150,000 mile guarantee.
Pros
- Mix ratios stated for -34 to 265F at 50/50
- Hybrid organic acid technology fights rust, scale and corrosion
- 5 year/150,000 mile guarantee
- Protects all cooling system metals, including aluminum
Cons
- Concentrate: it must be mixed with water before use
- No ready-to-use 50/50 version is stated
- Mixing needs clean tap water or demineralized water
- No shelf-life figure is stated
Genuine Coolant Antifreeze, 50/50 68163849AB
A 1-gallon 50/50 coolant, part number 68163849AB, with a 12-month, 10,000-mile limited warranty.
Pros
- 50/50 pre-mixed, ready to use
- 12 Months, 10,000 Miles Limited Warranty
- Contains a bittering agent
- Genuine Mopar part with a stated part number
Cons
- No freeze or boil-over figures are stated
- No color is stated
- No service-life figure is stated
- No mix or use guidance is stated in the listing
Honda Genuine Extended Life Antifreeze/Coolant
A 1-gallon blue 50/50 pre-diluted coolant, ready to use, with a service life of up to 5 years or about 60,000 miles.
Pros
- 50/50 pre-mixed, ready to use
- Service life up to 5 years or about 60,000 miles
- Protects metal and non-metal parts against corrosion and rust
- Matches factory fill for Honda systems requiring Type 2
Cons
- Manufacturer warranty does not apply to fluids
- No freeze or boil-over figures are stated
- Type 2 only: check the manual for the right coolant
- No concentrate option is stated
Can you use water as engine coolant? What water does and does not do
Water is the mixing half of coolant, not the coolant itself. The Zerex concentrates mix with clean tap water or demineralized water at a 50/50 ratio, and the mix is what gives the protection: freeze protection and boil-over resistance, plus additives that resist rust, scale and corrosion. Straight water has none of that. The Honda, Zerex and Mopar listings all state a bittering agent; straight water has none.
The right mix: 50/50, 60/40 and 70/30
The Zerex listings state three mix ratios, all with clean tap water or demineralized water. At 50/50 the mix covers temperatures from -34 to 265F, at 60/40 it covers -62 to 270F, and at 70/30 it covers -84 to 267F. The 50/50 ratio is the standard mix. Pre-mixed coolants skip this step entirely: the Honda Type 2 and the Mopar are both 50/50 and ready to use.
Pre-mixed or concentrate
Pre-mixed coolant is the simple choice: open the jug and pour. The Honda Type 2 is a 50/50 pre-diluted blue coolant with a service life of up to 5 years or about 60,000 miles under normal conditions, and the Mopar is a 50/50 coolant with a 12-month, 10,000-mile limited warranty. Concentrate is the flexible choice: the Zerex Dex-Cool and G05 are 1-gallon concentrates that mix with water at the ratio the listing states, and both carry a 5 year/150,000 mile guarantee.
Match the coolant to the car
Coolant is not one-size-fits-all. The Honda Type 2 replaces part number OL999-9011 and matches factory fill for Honda systems requiring Type 2 coolant, while the Mopar is part number 68163849AB. The Zerex Dex-Cool is an orange concentrate with organic acid technology, and the Zerex G05 is a yellow concentrate with hybrid organic acid technology. Check the manual for the coolant type the car needs, and match the type, not just the jug size.
Coolants for the job: the gear in this guide
The coolants below cover the choices in this guide, from the ready-to-use 50/50 jugs to the concentrates you mix with water, so you can match the coolant to the car and the mix to the weather.
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FAQ: garage tools
Can I use water as engine coolant?
Water is one half of the mix, but straight water gives no freeze protection, boil-over resistance or corrosion protection. The Zerex listings state a 50/50 mix with water for protection from -34 to 265F, so use the mixed coolant, not water on its own.
Can I top up coolant with water?
Water goes in as part of the mix, not on its own. The Zerex concentrates mix with clean tap water at a 50/50 ratio, and the Honda Type 2 and the Mopar are pre-mixed 50/50 coolants that are ready to use.
What is the difference between pre-mixed and concentrate coolant?
Pre-mixed 50/50 coolant is ready to use, while concentrate mixes with clean tap water or demineralized water at the ratio the listing states. The Honda Type 2 and the Mopar are pre-mixed, and the Zerex Dex-Cool and G05 are concentrates.
How long does coolant last?
The Honda listing states up to 5 years or about 60,000 miles under normal conditions, and the Zerex listings state a 5 year/150,000 mile guarantee. The Mopar listing states a 12-month, 10,000-mile limited warranty.
Which coolant does my car need?
Check the manual. The Honda Type 2 matches factory fill for Honda systems requiring Type 2 coolant, the Mopar is part number 68163849AB, and the Zerex Dex-Cool and G05 are orange and yellow concentrates.
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