Why Winter Is the Best Time for a Coolant Flush
Author: Toby Date Posted:20 June 2025
Cold mornings, frosty windscreens, and that first crank of the engine... Winter isn't just hard on drivers — it’s hard on your engine too. And if your coolant system isn’t up to scratch, you could be setting yourself up for trouble when the temps drop.
Let’s break down why winter is the ideal time to flush your coolant, the signs you shouldn’t ignore, and what coolants are right for your car.
How Often Should a Coolant Filter Be Changed?
Most coolant filters should be replaced every 20,000 to 40,000 km, depending on your vehicle. Winter’s a great time to do it, as a clean filter ensures proper coolant flow, prevents blockages, and protects your engine from corrosion and overheating during cold starts.
Why Cold Weather Stresses Your Cooling System
It’s a common misconception that coolant (or antifreeze) only protects your engine from overheating in summer. In reality, coolant also prevents your engine and radiator from freezing, while helping the system maintain proper heat distribution — especially critical on cold starts.
Low temps make your engine work harder to reach operating temperature. If your coolant is old, contaminated, or too diluted, you risk:
- Overheating (yes, even in winter!)
- Poor heater performance
- Damage to seals, hoses, and the radiator itself
Signs Your Coolant Is Overdue
If your car’s been showing these warning signs, it’s probably time for a flush:
- Heater not blowing hot air
- Engine running hotter than normal, even on cold days
- Coolant looks rusty, cloudy, or has debris inside the reservoir
- Sweet smell inside the car (a sign of possible coolant leaks or heater core issues)
Will a Car Run Better After a Coolant Flush?
Yes, because flushing your coolant removes sludge, rust, and old fluid that can block passages and reduce cooling efficiency. A clean system allows your engine to reach and hold its optimal operating temperature more easily, improving fuel efficiency, performance, and protecting key components from overheating, wear, and costly damage.
The Coolant Flush Process (Simplified)
Here’s a quick breakdown of the coolant flush process:
- Let the engine cool completely.
- Drain the old coolant from the radiator and block.
- Flush the system using a radiator flush solution or clean water.
- Refill with the correct coolant type and mix ratio (usually 50/50 coolant and demineralised water).
- Bleed the system to remove air pockets.
- Check for leaks and monitor coolant levels after the first few drives.
Pro Tip: Always dispose of old coolant safely at your local recycling centre — it's toxic to people, pets, and the environment.
Common Coolants and Which One Is Right for You
Not all coolants are created equal. Here’s a quick cheat sheet:
- Green coolant - Traditional glycol-based, usually changed every 2 years or 40,000 km.
- Red coolant (OAT) - Organic Acid Technology, longer-lasting, up to 5 years or 250,000 km.
- Long-Life Coolant (LLC) - Hybrid coolants offering extended protection for modern engines.
Check if your system uses a coolant filter (common in diesel engines). Wondering "How often should a coolant filter be changed?" Generally, every 20,000–40,000 km depending on your setup — and winter is the perfect time to swap it out.
Do Cars Really Need a Coolant Flush?
Absolutely. Over time, coolant breaks down and loses its protective properties. It becomes acidic, corrodes your radiator and internals, and can even clog passages. Especially in colder months when your engine’s cooling system is working overtime to maintain balance. Flushing out the old coolant clears debris, restores proper flow, and ensures your engine stays healthy year-round.
Keep Your Engine Winter-Ready with Superspares
Winter’s the perfect excuse to tick off a coolant flush as part of your regular service essentials. At Superspares, your trusted automotive parts store, we stock everything you need — from coolants and flush kits to coolant filters and hoses, all matched to your vehicle.
Browse our huge range online, get it delivered Australia-wide, and keep your engine protected, no matter the weather.
