A coolant flush (also called a radiator flush or coolant exchange) is one of the cheapest ways to protect one of the most expensive systems in your car. Engine coolant — antifreeze mixed with distilled water — carries heat away from the engine, prevents freezing in winter, and inhibits corrosion inside the radiator, heater core, water pump, and hoses. Over time it breaks down, turns acidic, and loses those abilities, which is why manufacturers recommend a flush every 30,000 to 100,000 miles depending on the coolant type.
This calculator turns the line items on a repair invoice into one number: what a coolant flush should actually cost you. It adds the price of the coolant itself, the total capacity of your cooling system, the shop's flush labor, and local sales tax, so you can compare a written quote against a fair range before you authorize the work. Adjust the sliders and the result card updates instantly.
How to Use
- Enter the Coolant Price (per Gallon). If the shop uses conventional green antifreeze, expect roughly $10–$20 per gallon. If your car requires extended-life coolant — the orange, pink, red, or purple OAT/HOAT stuff that many modern vehicles specify — budget $20–$30 per gallon. Using the wrong coolant can damage seals and the water pump, so match the bottle to your owner's manual.
- Set the Coolant Capacity in gallons. Most four- and six-cylinder passenger cars hold about 1.5–2 gallons, while full-size trucks, SUVs, and performance cars often hold 3–5 gallons. Your owner's manual lists the exact refill volume.
- Type the Flush Labor the shop quoted. A basic drain-and-refill runs about $100–$200; a pressure-machine reverse flush at a dealership can run $150–$250. You can also enter $0 here if you plan to do the work yourself and only want to price the fluid.
- Add the Sales Tax rate for your area. Parts are almost always taxed; labor often is not, but entering your local combined rate gives you a realistic all-in total. If tax on labor does not apply where you live, you can lower the number slightly.
The result card splits the bill into coolant parts, labor, and tax, then shows the total flush cost. If you are comparing two shops, run each quote through the same inputs so the comparison is apples to apples.
How the Cost Is Built
A coolant flush invoice has only three moving parts, and this calculator follows them exactly:
- Coolant parts = price per gallon × system capacity. A 3-gallon system at $20/gallon means $60 of fluid.
- Labor = the shop's charge for draining the old coolant, refilling, burping air from the system, and running the engine to operating temperature.
- Sales tax = applied to the subtotal at your local rate.
Worked example at the defaults: 3 gallons × $20 = $60 in coolant, plus $150 labor = $210 subtotal. At an 8% sales tax that adds $16.80, for a grand total of $226.80. That is the typical price range for a sedan at an independent shop. A dealer using a flush machine and a larger truck with extended-life coolant can push the same job toward $300–$400.
What Does a Coolant Flush Actually Include?
Not every "flush" is the same, and the price reflects it. A simple drain-and-fill removes only about two-thirds of the old coolant because the block and heater core trap the rest. A power-flush machine reverses flow through the radiator and pushes out nearly all of the old fluid, and it often includes a chemical cleaner and a new bottle of coolant conditioner. If a quote seems unusually cheap, ask whether it is a drain-and-fill or a full reverse flush — the latter is the service the higher prices pay for.
Most manufacturers also recommend replacing the thermostat and pressure cap during a flush on higher-mileage cars, and always swapping in new coolant when the system is open. These add-on parts are cheap ($10–$40 each) but can double the life of the cooling system.
DIY vs. Professional Flush
Doing it yourself is almost always cheaper. A 50/50 premixed gallon costs $12–$20 at any auto parts store, and a typical car needs two jugs — about $30–$40 of fluid total. The catch is disposal: old coolant is toxic and cannot go down the drain or onto the ground; almost every parts store and municipal yard takes it back for free. A DIY drain-and-fill does not fully purge the block, so you may need to repeat it after a few hundred miles to get closer to a full flush.
A professional flush costs more because of the labor and the machine, but it does a more complete job in one visit and leaves less air in the system. Use this calculator to see the trade-off: if the labor line dwarfs the parts line and your car is out of warranty, a DIY job plus a later professional flush is often the smartest money.
Examples
Example 1 — Average sedan at an independent shop. A 4-cylinder car holds 2 gallons, the shop uses conventional coolant at $15/gallon, labor is $120, and local tax is 8%. Coolant parts are $30, subtotal is $150, tax is $12, and the total is $162. This is a fair, mid-range quote.
Example 2 — Truck with extended-life coolant. A V8 pickup holds 4 gallons, the dealer charges $28/gallon for OEM-approved HOAT coolant, and flush labor is $220. Parts are $112, subtotal is $332, at 8% tax that is $26.56, for a total of $358.56. If you are quoted less than $250, confirm whether they are using the correct spec coolant.
Example 3 — DIY flush. Enter a labor cost of $0, a 2-gallon system at $15/gallon, and 0% tax. The result is $30 — just the fluid. Add a $15 new radiator cap and a $25 thermostat, and you still finish well under $100.
FAQ
How much does a coolant flush cost?
Most drivers pay between $150 and $300 for a professional coolant flush. The exact number depends on your cooling system's capacity (1.5–5 gallons), the type of coolant ($10–$30 per gallon), and the shop's labor ($100–$250). Use the calculator above to price your own car with your local quotes.
Is a coolant flush the same as a radiator flush?
Yes, in everyday shop language the two terms are used interchangeably. Technically a radiator flush describes pushing fluid through the radiator, while a coolant flush covers the entire cooling system — radiator, engine block, heater core, and hoses. Both typically mean the same drain, refill, and bleed service.
How often should I flush my coolant?
Follow your owner's manual. Conventional green coolant usually needs a change every 30,000 miles; extended-life OAT/HOAT coolant can last 100,000 to 150,000 miles. Signs you are overdue include rust-colored or gritty coolant, a sweet smell inside the cabin, or the engine running hotter than usual.
Can I do a coolant flush myself?
Yes. Drain the old coolant from the radiator petcock, refill with a 50/50 mix of antifreeze and distilled water, burp the air, and run the engine. Expect to remove only about two-thirds of the old fluid in one pass, so repeat after a few hundred miles. Always recycle old coolant at an auto parts store — never pour it on the ground or down a drain.
What happens if I skip a coolant flush?
Old coolant turns acidic and loses its corrosion inhibitors, which can eat away at the radiator, heater core, water pump impeller, and gaskets. A clogged heater core or a failed water pump costs $500–$1,500 to fix — far more than a $200 flush. The flush is cheap insurance against a very expensive repair.
Does a coolant flush improve gas mileage?
Coolant itself does not directly change MPG, but an overheating engine runs less efficiently and can trigger the computer to enrich the fuel mixture. Keeping the cooling system clean and at the correct temperature helps the engine stay in its optimal operating range, which supports — but does not guarantee — better fuel economy.
Disclaimer
This coolant flush cost calculator is provided for informational purposes only and does not constitute mechanical, repair, or financial advice. Estimates are based on the inputs you enter and a simple parts-plus-labor invoice model; actual prices vary by region, shop, vehicle make and model, coolant specification, and local tax rates. Always confirm the exact coolant type, system capacity, and final price directly with a qualified automotive technician before authorizing service.