📋 Quick Answer
IAT (Green)
Every 30k mi / 2 yr
OAT (Orange/Pink)
Every 100k mi / 5 yr
HOAT (Yellow)
Every 100k mi / 5 yr
Always Check
Color, clarity, smell
Flush your coolant every 60,000 to 100,000 miles or every 5 years, whichever comes first. Conventional green IAT coolant needs replacement every 30,000 miles or 2 years. Extended-life OAT and HOAT coolants (orange, pink, blue) last 100,000 miles or 5 years. If your car sits a lot or you live in extreme climates, flush sooner. Look at the actual coolant color and clarity every oil change as a sanity check.
🔍 Detailed Breakdown
#1
Conventional IAT (Green) Coolant
Found on pre-1996 GM, Ford, and most older vehicles. Inhibitors deplete fast. Flush every 30,000 miles or every 2 years. Mixing with other coolant types gels into sludge.
100%
Cost
$70–$150
DIY
Easy
Severity
Strict interval
#2
OAT (Orange, Red, Pink) Coolant
Dex-Cool, Toyota Long Life, VW G12. Found on 1996+ GM, most Toyotas, VW, Audi. Flush every 100,000 miles or 5 years. Lasts longer thanks to organic acid inhibitors.
100%
Cost
$100–$200
DIY
Moderate
Severity
Standard interval
#3
HOAT (Yellow, Turquoise) Coolant
Found on Chrysler, Ford post-2002, Mercedes, BMW. Blends silicate and OAT inhibitors. Flush every 100,000 miles or 5 years. Do not mix with green or pink coolant.
100%
Cost
$100–$200
DIY
Moderate
Severity
Standard interval
#4
Asian Blue or Pink Coolant
Honda Type 2, Toyota Super Long Life. Pre-mixed by the manufacturer, often skipped at indie shops. Flush every 60,000 miles for first replacement, then every 100,000 miles.
100%
Cost
$100–$200
DIY
Moderate
Severity
Use OEM coolant
#5
Severe Service Reduces Interval by Half
Towing, mountain driving, lots of short trips, or extreme heat shortens coolant life. Cut the recommended interval roughly in half if you fit any of these conditions.
80%
Cost
$100–$200
DIY
Moderate
Severity
Adjust interval
#6
Always Check Color and Clarity at Each Oil Change
Open the reservoir, look at the fluid. If it has darkened from its original color, gone cloudy, or has visible particles, flush now even if you have not hit the mileage interval.
100%
Cost
Free
DIY
Easy
Severity
Visual inspection
🔗 Related Guides
❓ Frequently Asked Questions
Is it OK to flush coolant every 30,000 miles?
Yes if you have green IAT coolant or older vehicle. For modern OAT or HOAT systems, every 30,000 is overkill but not harmful. Most owner manuals specify 60,000 to 100,000 miles for these.
What happens if I never flush my coolant?
Corrosion inhibitors deplete, rust forms in the block, the water pump impeller corrodes, and the heater core clogs. Total preventable damage usually runs $2,000 to $3,000 over the life of the car.
How do I know what coolant my car uses?
Check the owner manual, the coolant cap, or look it up by VIN. Never guess by color: green could be IAT or modified OAT, and they are incompatible. Match the spec, not the color.
Can I just top off coolant instead of flushing?
Topping off is fine between flushes. It does not reset the maintenance interval because the inhibitors in the old coolant are still depleting on their own schedule.
Does the type of water matter?
Yes. Use distilled water only. Tap water has minerals that form scale in the system, shortening the life of the new coolant and clogging the radiator.
Should I have my flush done at the dealer?
Not required. Any competent shop can flush a cooling system. The key is using the correct coolant for your vehicle. Bring your own if you are unsure what they stock.