How do I winterize my marine engine in the boat: Tips and guidelines

Regularly replacing the coolant in your Volvo Penta engine is crucial. Failure to do so could result in cooling problems and costly repairs.

Coolant for Volvo Penta engines: Everything you need to know!

Which coolant should I use for my Volvo Penta engine? We get this question a lot at MarineDustrie . In this blog post, we'll tell you everything you need to know about the different types of Volvo Penta coolant , how to use it, how to replace it, and how often to change it.

Table of contents:
1. Why Coolant is Critical
2. What is coolant and what does it do?
3. How do I choose the right coolant for my Volvo Penta engine? -> Handy search tool
4. When and how often should you change coolant?
5. Step-by-step: Checking and topping up coolant
6. Overview per engine: correct type and capacity (liters)
7. Frequently Asked Questions (FAQ)
8. Safety, environment & warranty
1. Why Coolant is Critical
- Prevents overheating and cavitation
- Protects against corrosion (engine block, heat exchanger, pumps, pipes)
- Lubricates the circulation pump
- Increases boiling point and lowers freezing point
2. What is coolant and what does it do?
Base: water + ethylene glycol/propylene glycol

Additive packages: IAT / OAT / HOAT

OEM Specifications Volvo Penta (VCS/VOA: VCS-2 (Yellow) and Coolant-Ready-Mixed (Green) Non-OAT
3. How do I choose the right coolant for my Volvo Penta engine?
Always refer to the OEM specification on the nameplate/manual -> Refer to our search tool.
- Do not mix different coolants
- Color ≠ specification (color is an indication, but not binding)
- Environmental conditions: frost protection down to –25 °C / –36 °C
- Mixing ratio: 40/60 vs 50/50 (Volvo Penta coolants are ready to use and do not require dilution!
4. When and how often should I replace the coolant?
- Volvo Penta coolant should be replaced every 2-4 years
- Replace immediately in case of: rust/sludge, discoloration, unknown mix, or if you are performing maintenance on the cooling circuit
- Caution! Never mix two different coolants together. Mixing OAT and EG coolants can cause excessive sludge formation.
5. Step-by-step: Checking and topping up coolant
- Always check the coolant level when the engine is cold!
- Check expansion tank level (MIN–MAX)
- Refractometer/hydrometer: measuring freezing point
- Top up with the same specification and correct dilution
- Bleeding: open/warm up high points and recheck level
7. Frequently Asked Questions (FAQ)
Can I mix green and yellow/green coolant? → No, always flush when changing.
Is color the leading factor? → No, follow OEM specifications.
How do I measure freezing point? → Refractometer.
What if I don't know what's in it? → Use a full rinse and the correct specification.
8) Safety, environment & warranty
- Use collection container, dispose of old coolant as chemical waste
- Do not discharge into bilge or environment
- Please note the warranty conditions in case of incorrect specifications