How to top up coolant on a Subaru?

To top up coolant on a Subaru, use a Subaru-approved long-life coolant (usually premixed 50/50 with distilled water) and fill the expansion reservoir only when the engine is cold. This approach protects the cooling system and reduces the chance of scalding injuries.

This guide explains how to check your coolant level, what coolant to use, and the step-by-step process to top off the system safely. It also covers model-specific quirks, safety tips, and what to do if you notice leaks or overheating.

What coolant to use and why

Choosing the correct coolant is essential for preventing corrosion, freezing, and overheating. Subaru engines typically require a silicate-free long-life coolant (organic acid technology, or OAT). Use Subaru Genuine Coolant or an equivalent that is specifically designed for Subaru engines. Do not mix different coolant chemistries or brands, as that can reduce cooling efficiency and cause deposits or corrosion.

• Subaru Genuine Long-Life Coolant or an equivalent, silicate-free OAT coolant


• Distilled water (only if you’re mixing concentrate yourself)


• A clean funnel to avoid introducing debris


• Gloves and rags for spills and safety


• Optional coolant tester or hydrometer if you’re mixing concentrates

Using the correct coolant protects the engine and helps maintain the warranty. For many drivers, premixed 50/50 coolant is the easiest and cleanest option, but always follow the product label and your owner's manual.

Tools and materials you’ll need

Before you begin, gather the necessary items to ensure a clean, safe refill and to avoid wasting coolant.

• Subaru Genuine Long-Life Coolant or approved equivalent


• Distilled water (if using concentrate)


• Clean funnel


• Clean cloths or paper towels


• Gloves and eye protection


• Flashlight if you need better visibility under the hood

Having the right tools on hand helps you avoid spills, ensures the correct 50/50 mix when needed, and makes the process smoother.

Step-by-step topping-up process

Follow these steps to safely top up your Subaru’s coolant. The procedure works for most recent Subaru models with a translucent expansion tank, though exact locations can vary by year and model.

1. Park on level ground and turn off the engine. Allow the engine to cool completely before touching the cooling system.


2. Open the hood and locate the expansion (coolant) reservoir. It’s usually a translucent tank with MIN and MAX marks near the radiator.


3. Carefully remove the reservoir cap only when the system is cool. If your model has a radiator cap separate from the reservoir, do not remove it while hot.


4. Check the current coolant level. If it’s between MIN and MAX, you may not need to add coolant yet. If it’s below MIN, you’ll add coolant.


5. Prepare the coolant: if you’re using a premixed coolant, you can pour directly. If you have concentrated coolant, mix it 50/50 with distilled water as recommended on the label.


6. Slowly pour coolant into the expansion reservoir until the level is at or just below the MAX line. Avoid overfilling.


7. Secure the reservoir cap firmly (and any radiator cap if applicable) after topping up.


8. Start the engine and allow it to reach normal operating temperature with the heater on hot. This helps circulate coolant and purge air from the system.


9. Turn off the engine and let it cool completely again, then recheck the level. Top off to MAX if needed. Do not mix in additional coolant while the engine is hot.


10. Check for leaks around hoses, clamps, and the radiator. If you notice a leak or if the level drops quickly, have the system inspected by a professional.

After completing these steps, you should have a stable coolant level and a cooler engine temperature profile. If the level remains stubbornly low, there may be a leak or a degraded hose that requires service.

Model-specific considerations

Subaru models can differ in how the cooling system is accessed. Here are notes to help you navigate common variations by generation and configuration.

Modern Subarus (approximately 2010s onward) with expansion tank

Most newer Subarus use a closed expansion tank system. The reservoir is the primary point for topping up. In these models, you typically should not try to open or top up through the radiator cap. Use only the approved coolant in the expansion tank and keep the level between MIN and MAX.

Older Subarus and some performance variants

Some older models or certain trims may have a more traditional setup with a radiator cap separate from the expansion tank. If you encounter a radiator cap, follow the same safety rules: ensure the engine is cold, and only open the cap when safe. Always refer to your specific owner’s manual for exact procedures, as some models may require a different bleed or fill method.

Safety and maintenance tips

Handle coolant with care. It is toxic if ingested and can cause skin and eye irritation. Store coolant out of reach of children and pets, and dispose of used coolant at an authorized recycling facility. Regularly check coolant levels, and replace coolant according to Subaru’s maintenance schedule or your manual (often every 5 years or 100,000 miles, depending on the region and product). If you notice overheating, white smoke, or a milky appearance in the oil, stop driving and seek professional service promptly.

What to do if you notice problems

If topping up doesn’t resolve overheating or the level continues to drop, there may be a leak, faulty thermostat, radiator, hose, or water pump. Do not drive for extended periods with low coolant. Have a qualified technician inspect the cooling system to identify leaks, air pockets, or internal problems such as a head gasket issue.

Summary

To top up coolant on a Subaru, use a Subaru-approved long-life, silicate-free coolant (usually a premixed 50/50 solution) and fill the expansion reservoir when the engine is cold. Gather the right tools, verify the correct coolant type, and follow a careful, step-by-step process to avoid overfilling or introducing air. Pay attention to model-specific setups, safety precautions, and signs of leaks. When in doubt, consult the owner’s manual or a trusted technician to ensure you’re using the correct coolant and filling method for your exact model and year. Regular checks help prevent overheating and protect the cooling system over time.

Can I just pour coolant into the reservoir?

Yes, you can pour coolant directly into the reservoir to top it off, but it's important to make sure the engine is cool first and that you are using the correct type of coolant. Pour the coolant up to the "cold fill" line on the reservoir, and check the level a few times after the engine cools down, as the system may draw more from the reservoir over time. If you've completely run out of coolant, it's best to also pour some directly into the radiator if it has a cap to ensure the system is full, and follow your car's specific instructions for bleeding air from the system.
 
This video demonstrates how to check and add coolant to your car's reservoir: 1m2CarProsYouTube · Oct 6, 2016
How to top off coolant in the reservoir

• Ensure the engine is cool. Wait for the engine to be completely cool to avoid personal injury and potential damage to the cooling system. 
• Open the hood and locate the reservoir. It's typically a plastic tank near the radiator with "min" and "max" or "cold" and "hot" lines on the side. 
• Loosen the cap slowly. Be cautious, as there may be residual pressure. 
• Add the correct coolant. Pour the appropriate coolant mixture until it reaches the "cold fill" line on the reservoir. 
• Replace the cap. Tighten it securely, usually until you hear a click. 
• Monitor the level. After a few driving cycles, check the level again when the engine is cold. It's normal for the level to drop slightly as air is pushed out of the system, so top it off again if needed. 

Important considerations

• Use the right type of coolant. Make sure to use the specific coolant recommended by your car's manufacturer to prevent corrosion and damage. 
• Don't use plain water for extended periods. While water can be used in a pinch, using it long-term can lead to corrosion and overheating. 
• If the system is completely empty, use the radiator. If your car has a pressure cap directly on the radiator, you may want to pour some coolant directly into the radiator first to ensure the system is fully filled. 

You can watch this video to learn about the proper way to add coolant to your car's radiator: 1mEngineering ExplainedYouTube · Jun 22, 2016

Can I top up engine coolant myself?

You can absolutely refill the coolant yourself if it's below the ``min'' line. Just be aware of two things:

How to refill coolant on a Subaru?

To add coolant to a Subaru, first ensure the engine is completely cool and the car is parked on a level surface. Check the coolant level in the overflow reservoir, which is a white plastic tank with "low" and "full" marks. If the level is below the "full" mark, add the correct Subaru-specific coolant to reach the line. If the overflow tank is empty or you've drained the system, you may need to also open the radiator cap (again, only when cool) and fill it to the top before filling the reservoir. 
This video demonstrates how to check and add coolant to a Subaru Forester: 59sSUBARU DRIVESYouTube · Nov 14, 2025
Step 1: Prepare the vehicle 

• Park the Subaru on a level surface. 
• Let the engine cool down completely. Do not open the radiator cap or reservoir while the engine is hot. 

Step 2: Locate the coolant reservoir 

• Find the translucent white plastic coolant reservoir tank, often with "low" and "full" marks on the side. 

You can watch this video to see the location of the coolant reservoir on a Subaru Crosstrek: 35sDIY PintoYouTube · Nov 13, 2017
Step 3: Check and fill the reservoir 

• If the coolant level is below the "full" line, add the correct Subaru coolant (or an equivalent) to the "full" mark. 
• Replace the cap securely after adding coolant. 

Step 4: Check the radiator (if necessary)

• If the reservoir is empty, you may need to fill the radiator itself as well. 
• Caution: Only open the radiator cap on a cool engine. Press down on the cap and turn it to the left to release it. 
• Fill the radiator with the correct coolant until it is near the top. 
• Replace the radiator cap and tighten it securely. 

Important safety and general tips

• Use the right coolant: Always use the specific coolant recommended for your Subaru model to avoid damage. 
• Avoid mixing: Never mix different types of coolant, as this can cause problems. 
• Be careful with spills: Coolant is toxic, so wipe up any spills and dispose of coolant properly. 
• Look for leaks: If you need to add coolant frequently, it could indicate a leak. It's best to have your Subaru checked by a professional. 
• Dashboard light: If the low coolant warning light comes on, have your car inspected soon to prevent engine damage. 

When to add coolant to Subaru?

When: Every Fuel Stop. Check your car's coolant level on the outside of the reservoir while the engine is cool. If the level is close to or lower than the "LOW" mark, add coolant up to the "FULL" mark. If the reserve tank is empty, remove the radiator cap (Do not open when the radiator is hot!) and refill as required.