What Coolant Does a 2018 Audi A4 Use?

The 2018 Audi A4 is designed to use a pink or purple, phosphate-free, silicate-free OAT (Organic Acid Technology) coolant that meets the VW/Audi G12++ or G13 specification, typically sold as Audi/VW Genuine Coolant/Antifreeze. Mixing it with generic green or “universal” coolant is not recommended and can damage the cooling system.

Understanding the Coolant Specification for the 2018 Audi A4

The question of which coolant to use in a 2018 Audi A4 is more complex than simply naming a color or brand. Audi, like most modern European manufacturers, specifies a very particular chemical formulation. Using the correct coolant helps prevent corrosion, overheating, and premature failure of key components such as the water pump, radiator, and heater core.

Official Audi/VW Coolant Specs

Audi uses its own internal coolant standards, labeled with “G” codes. These standards define not only the antifreeze base, but also the anti-corrosion additives and compatibility with aluminum and mixed-metal engines and radiators.

The following list outlines the main coolant specifications relevant to a 2018 Audi A4 and how they relate to products you can buy today.

• G12++ (TL-VW 774 G): Pink or purple OAT coolant, phosphate- and silicate-free; long-life, designed for aluminum engines and modern cooling systems.
• G13 (TL-VW 774 J): Typically purple or pink, based on a glycerin/ethylene glycol mix with environmentally friendlier additives; backward compatible with G12++ in most applications.
• Factory fill for 2018 A4: In most markets, the factory coolant is equivalent to G12++ or G13. Either Audi/VW Genuine Coolant labeled G12++ or G13 is acceptable, provided it is mixed correctly with distilled water.
• Pre-mixed vs. concentrate: Audi/VW coolants are sold as both ready-mix (usually around 50/50) and concentrate that must be diluted; always check the label.
• Color as a guideline, not a guarantee: While G12++/G13 are usually pink or purple, color alone is not a reliable indicator of compatibility; always verify the VW spec on the bottle.

Together, these specifications ensure that the coolant in your 2018 Audi A4 is compatible with the metals, gaskets, and plastics in the engine and cooling system, and that it will deliver the long service life Audi engineered.

Where to Find the Correct Coolant Information for Your Car

Although the general specification for the 2018 Audi A4 is clear, individual cars may have regional variations or dealer practices. It’s wise to verify the exact spec for your vehicle rather than relying solely on color or generic labels.

The following sources can help you confirm the appropriate coolant for your specific 2018 Audi A4.

• Owner’s manual: Contains a section on engine coolant specifying VW standard (e.g., “Use only coolant that meets VW TL-VW 774 G/J”).
• Coolant expansion tank cap or sticker: Many Audi models have the G-code or a reminder to use “Audi-approved coolant” printed near the reservoir.
• Dealer service department: A franchised Audi dealer can look up the exact part number of the coolant specified for your VIN.
• Official Audi parts catalog: Online Audi/VW parts sites list the correct coolant by model year and engine code.
• Service history: If the car has been serviced at an Audi dealer, the coolant type used is usually listed on invoices or service records.

Consulting these sources helps ensure you match or maintain the original coolant specification, rather than guessing based on appearance or generic labels.

Compatible Aftermarket Coolants

Not every driver has easy access to Audi-branded coolant, especially outside large dealerships or major cities. Some aftermarket brands manufacture coolants that explicitly state compatibility with VW G12++ or G13 standards.

The list below highlights key criteria and examples to consider if you must use an aftermarket product.

• VW/Audi approval on the label: Look for clear wording like “Meets or exceeds VW TL-VW 774 G/J” or “Suitable for VW/Audi G12++/G13 applications.”
• OAT or HOAT formulation: It should be an OAT (or compatible HOAT) formula, silicate- and phosphate-free, designed for European aluminum engines.
• Brand examples: Products from reputable manufacturers (e.g., Pentosin, Febi Bilstein, Zerex G40) often list VW G12++/G13 compatibility; verify updated labels, as formulations change over time.
• Avoid generic “universal” coolants: Many “universal” or “compatible with all makes” products rely on compromise formulations that may not fully protect Audi systems long-term.
• Check local climate needs: Ensure any compatible coolant can be mixed to reach a freezing point at least to −25°C (−13°F) or lower, depending on your climate.

While these aftermarket options can work when they meet VW/Audi specs, using genuine Audi/VW coolant remains the safest choice to avoid compatibility and warranty concerns.

Mixing, Dilution, and Top-Up Practices

Using the correct coolant is only part of the equation; how you mix and top it up significantly affects cooling performance and system longevity.

Correct Coolant Mixture

Audi cooling systems are typically designed around a 50/50 mix of coolant concentrate and water, but this can vary slightly depending on climate. The dilution level affects both freeze protection and boiling point.

The following steps describe how to achieve an appropriate coolant concentration for a 2018 Audi A4.

1. Use distilled or deionized water: Tap water can introduce minerals that cause scale and deposits within the cooling system.
2. Target a 50/50 mix: For most climates, a 1:1 ratio of coolant concentrate to water offers freeze protection down to about −35°C (−31°F) and adequate corrosion protection.
3. Adjust for extreme climates: In very cold regions, you may go up to around 60% coolant / 40% water, but never exceed the manufacturer’s recommended maximum; too much concentrate can reduce heat transfer.
4. Pre-mixed products: If using a pre-mixed (ready-to-use) coolant labeled for VW G12++/G13, do not add extra water.
5. Measure, don’t guess: When filling a largely empty system, measure quantities to ensure the target ratio, rather than adding random amounts of concentrate and water.

By paying attention to the concentration, you ensure that your Audi A4’s coolant provides both proper temperature protection and long-term corrosion resistance.

Safe Top-Up Procedures

Many issues arise when owners top up older coolant with the wrong type or with plain water alone. Careful top-up practices help maintain the integrity of the original coolant mix.

The steps below outline best practices when topping up the coolant in a 2018 Audi A4.

1. Check coolant only when the engine is cool: Opening the expansion tank while hot can release scalding steam and pressurized fluid.
2. Identify what’s already in the system: If you’re unsure of the coolant type, avoid mixing random products; consider a full flush instead.
3. Use matching VW G12++/G13 coolant: Top up with the same spec coolant, ideally the same brand and type already in the system.
4. Small adjustments with distilled water only: If the level is just slightly low and the coolant concentration is known to be correct, you can add a small amount of distilled water, but don’t do this repeatedly.
5. Bleed air after major top-ups or changes: When adding substantial amounts of coolant or after a flush, follow the Audi bleeding procedure (often involving specific bleed screws and warm-up cycles) to prevent air pockets.

Following these top-up steps helps prevent dilution errors, air locks, and the chemical incompatibilities that can result from random mixing.

Risks of Using the Wrong Coolant

Choosing the wrong coolant for a 2018 Audi A4 can have consequences that are often delayed but expensive. The additives in non-approved coolants can react with Audi’s system materials and the existing coolant in unpredictable ways.

The list below summarizes key problems that can arise from using an incorrect or incompatible coolant type.

• Corrosion of aluminum components: Incompatible additives can fail to protect, or even accelerate corrosion in the cylinder head, radiator, and heater core.
• Deposits and sludge formation: Mixing G12++/G13 with older IAT (green) coolants or some “universal” blends can create gel-like sludge that impedes flow and clogs passages.
• Water pump and seal damage: Incorrect chemistries can attack water pump seals, leading to leaks, noise, and premature failure.
• Overheating and hot spots: Deposits and scale reduce heat transfer, causing localized hot spots that may contribute to head gasket issues over time.
• Potential warranty or goodwill issues: If Audi determines that non-approved coolant contributed to a failure, warranty coverage or post-warranty goodwill repairs may be denied.

These risks underscore why sticking to the G12++/G13 specification is not simply a brand preference, but a technical requirement for the long-term health of the engine and cooling system.

When and How Often to Change the Coolant

While OAT coolants such as G12++ and G13 are marketed as long-life formulas, they are not permanent. Over time, their corrosion inhibitors deplete, making periodic replacement necessary.

The following points outline general service expectations and considerations for coolant changes in a 2018 Audi A4.

• Consult the maintenance schedule: Many Audi schedules recommend coolant service roughly every 10 years or 150,000 km (about 90,000 miles), but this can vary by market and engine.
• Real-world practice: In harsher climates or on higher-mileage vehicles, some independent specialists advise changing coolant closer to every 5–7 years.
• Condition over time: Dark, rusty, or cloudy coolant, or visible sludge in the expansion tank, is a sign that a flush is overdue regardless of mileage.
• Full flush over partial drain: When switching to a known-compatible G12++ or G13, a thorough flush minimizes the risk of leaving behind incompatible residues.
• Record the service: Documenting the coolant type and date of change helps future owners or technicians maintain compatibility.

By observing service intervals and coolant condition, owners can preempt many cooling system failures that often surface only after several years of neglected maintenance.

Key Takeaways and Summary

The 2018 Audi A4 is engineered to use a specific pink or purple, phosphate- and silicate-free OAT coolant that meets VW/Audi G12++ or G13 specifications. The safest choice is Audi/VW Genuine Coolant labeled for these standards, mixed with distilled water to about a 50/50 ratio. While some high-quality aftermarket coolants advertise compatibility with G12++/G13, generic or “universal” coolants and traditional green formulas should be avoided, especially mixing them with the factory fill.

Verifying the correct specification in the owner’s manual, on the coolant reservoir, or with an Audi dealer helps ensure that top-ups and flushes maintain the correct chemistry. Proper mixing, careful top-up practices, and periodic replacement protect against corrosion, sludge, water pump damage, and overheating. In practical terms, using the right G12++/G13-spec coolant, in the right ratio, and replacing it on schedule is one of the simplest ways to preserve the reliability and longevity of a 2018 Audi A4’s engine and cooling system.