Glycol dilution table

Freezing points of ethylene and propylene glycol mixtures from 0 to 60 % by volume, with density, specific heat and viscosity at your fluid temperature.

Freezing points of glycol mixtures

The table lists the approximate freezing point of ethylene glycol (MEG) and propylene glycol (MPG) mixtures with water from 0 to 60 % by volume. The values are based on ASHRAE published data; the mass fractions are shown as well, because many product data sheets use per cent by mass. Glycol is denser than water, so 30 % by volume of ethylene glycol is about 32 % by mass.

Glycol by volume (%)	MEG by mass (%)	MEG freezing point (°C)	MPG by mass (%)	MPG freezing point (°C)
0	0.0	0.0	0.0	0.0
5	5.7	-1.6	5.2	-1.7
10	11.2	-3.7	10.4	-3.4
15	16.6	-6.1	15.5	-5.3
20	22.0	-8.9	20.6	-7.4
25	27.2	-12.2	25.6	-10.0
30	32.3	-15.9	30.6	-13.1
35	37.4	-20.1	35.6	-16.9
40	42.5	-24.9	40.4	-21.5
45	47.5	-30.6	45.3	-27.1
50	52.4	-37.2	50.1	-33.6
55	57.3	-44.3	55.0	-41.1
60	62.2	-51.4	60.0	-51.1

The freezing point in the table is the temperature at which the first ice crystals form. Below it, the mixture turns into a slush that can still flow for a while. The burst protection point, below which the expanding ice can damage pipes, is lower. For chillers and heat exchangers only the freezing point matters: slush blocks the narrow channels of a plate heat exchanger long before any pipe would burst.

How to use the tool

Select the glycol type and the concentration, and enter the fluid temperature. The tool shows the freezing point, the mass fraction, the density, the specific heat and the viscosity at that temperature, and compares viscosity and heat transport with plain water. If you enter a volume, it also gives the litres of glycol and water to mix. For the reverse question, which concentration you need for a given temperature, use the glycol calculator.

The viscosity effect

Viscosity is the hidden cost of glycol. At 0 °C, a 30 % ethylene glycol mixture is roughly two and a half times as viscous as water, and 40 % propylene glycol nearly seven times. Higher viscosity means:

• A higher pressure drop in pipes, valves and heat exchangers, so the pump delivers less flow or uses more energy.
• A lower heat transfer coefficient in the evaporator, so the evaporating temperature falls and the chiller efficiency drops.
• Laminar flow in small pipes and plate heat exchangers at low temperatures, which further reduces heat transfer.
• Slower venting, because air bubbles rise more slowly in a viscous fluid.

The effect grows quickly at low temperature. A 30 % ethylene glycol mixture that works well at 10 °C is more than twice as viscous at -10 °C. This matters for process chillers with low leaving temperatures and for systems that start up cold after a winter shutdown.

Reading the property values

The density and the specific heat decide how much heat a litre of fluid carries. Their product, compared with water, is shown as a percentage: a value of 91 % means the pump must move about 10 % more fluid for the same capacity at the same temperature difference. The viscosity ratio indicates how much harder the pump works and how much the heat transfer in the evaporator suffers. Both values change with temperature, so enter the real fluid temperature, not a design value from another part of the system.

Practical recommendations

• Choose the lowest concentration that gives the required protection with a margin of 3 to 5 K, but not less than about 20 % for MEG and 25 % for MPG.
• When converting a water system to glycol, check the pump curve and the chiller capacity with the new fluid. The flow often drops by 5 to 15 %.
• Use a refractometer with the correct scale for the glycol type and check the concentration at every service visit.
• Label the system with the glycol type, the concentration and the date of the last fill, so nobody tops it up with the wrong fluid.

If a laboratory test shows degraded inhibitors or contamination, the fluid should be replaced. Read more on our antifreeze fluids page.

Frequently asked questions

Is the concentration by volume or by mass?

The tool and the first column of the table use per cent by volume, which is how glycol is usually mixed on site. The mass fraction is shown next to it. Always check which one a product data sheet uses before comparing.

Why stop at 60 %?

Above roughly 60 % the freezing point of ethylene glycol rises again and the viscosity becomes very high. Mixtures stronger than 60 % have no practical use in chilled water systems.

How accurate are the freezing points?

They are approximate values for pure glycol and water. Commercial fluids with inhibitors differ by about 1 K. For critical systems, use the data sheet of the product and measure with a refractometer.

Can I use automotive antifreeze in a chiller?

No. Automotive products contain silicates and other additives that form deposits in heat exchangers, and they are not designed for long service intervals in industrial systems. Use an industrial heat transfer fluid.