What coolant does my Mercedes need?

Your Mercedes requires coolant meeting MB‑Approval 325.0, 325.2 or 325.3 — usually G48 or G05 formulation. Check your owner's manual or the expansion tank cap for the correct type. Modern models typically use G05 (yellow/green), while older models use G48 (blue/green).

Can I mix different Mercedes coolants?

No. G48 and G05 are not compatible — mixing them can cause sludge formation, block radiator passages, and lead to overheating. Always flush the system thoroughly with distilled water when switching coolant types, and never top up with an incompatible formulation.

What is the correct coolant mixing ratio for Mercedes?

The standard mixing ratio is 50/50 coolant to distilled water, which provides freeze protection down to approximately −37°C. Use distilled or deionised water only — tap water contains minerals that can cause scaling and corrosion.

How often should I change my Mercedes coolant?

The recommended change interval is 5 years or 100,000 miles, whichever comes first. Older models (pre‑2005) using G48 may require a 2‑year interval — always check your specific vehicle requirements. Old coolant loses its corrosion inhibitors and becomes acidic, damaging the cooling system.

What happens if I use the wrong coolant in my Mercedes?

Using the wrong coolant can cause corrosion of aluminium components, sludge formation in the radiator, premature water pump failure, and reduced heat transfer leading to overheating. These failures are expensive to repair — using the correct MB‑Approved coolant is essential.

Coolant Specification

Mercedes coolant must meet MB‑Approval 325.0, 325.2 or 325.3 — usually a G48 (ethylene glycol‑based) or G05 (hybrid OAT) formulation, depending on model year. The correct mixing ratio is 50/50 coolant to distilled water, which provides freeze protection down to approximately −37°C.

Change interval: 5 years or 100,000 miles, whichever comes first
System capacity: Varies by model — typically 8–15 litres total system capacity
Never mix different coolant types — G48 and G05 are not compatible and can form sludge
Last verified: February 2026

Full specification table, variant differences, common mistakes, and why correct coolant choice matters below.

The Specification Table

This table summarises the core coolant specification for Mercedes‑Benz vehicles. Figures are based on manufacturer workshop data and verified against independent specialist records.

Spec	Value
Approved coolant types	MB‑Approval 325.0 (G48), 325.2, 325.3 (G05), 326.0 (M10)
Base chemistry	Ethylene glycol + corrosion inhibitors (G48) / Hybrid OAT (G05)
Mixing ratio (standard)	50/50 coolant/distilled water
Freeze protection (50/50)	Approx. −37°C [ESTIMATED]
Boiling point (50/50)	Approx. 129°C (pressurised system) [ESTIMATED]
Change interval	5 years / 100,000 miles [ESTIMATED]
Typical system capacity	8–15 litres (varies by model and engine) [PLACEHOLDER — confirm per model]

Figures marked [PLACEHOLDER] or [ESTIMATED] require confirmation against the OEM workshop manual before this page goes live — flagged here deliberately rather than guessed.

Variant Differences

Mercedes coolant specification has evolved over time. This table highlights the key differences between older and newer formulations.

Period	Approval	Chemistry	Colour	Notes
Pre‑2005 (classic)	MB‑Approval 325.0	G48 (IAT — Inorganic Acid Technology)	Blue/Green	Older conventional coolant; requires 2‑year change interval
2005–2015 (mid)	MB‑Approval 325.2	G48 (improved)	Blue/Green	Longer life (5 years/100k); still G48‑based
2015–present (modern)	MB‑Approval 325.3 / 326.0	G05 (Hybrid OAT) / M10 (silicate‑free)	Yellow/Green / Violet	Extended life; compatible with aluminium engines and modern cooling systems

Always confirm the correct coolant type for your specific model and model year — using the wrong formulation can lead to corrosion, sludge, and premature water pump failure.

Notes & Caveats

Several factors can affect coolant specification and service life:

Never top up with tap water — minerals and chlorides can cause corrosion and scaling. Always use distilled or deionised water when mixing coolant.
Mixing G48 and G05 is not recommended — the different inhibitor chemistries can react, forming sludge that blocks radiator passages and heater cores. Flush the system thoroughly if switching types.
Some models use different coolants for the engine and the intercooler/charge air system — check your vehicle's specific requirements. [EM-INTERVIEW]
Coolant concentration should be checked with a refractometer — not a hydrometer, as glycol content affects the reading. Aim for 50/50, but adjust for extreme climates (e.g., colder regions may run 55/60% coolant).
Older Mercedes models (pre‑2005) require G48‑based coolant with a 2‑year change interval — the inhibitor package degrades faster than modern G05 formulations.

Common Mistakes

Using universal "all makes" coolant. These often do not meet MB‑Approval standards and can cause corrosion — especially on modern aluminium engines.
Topping up with neat coolant. This raises the freezing point and reduces heat transfer — always pre‑mix to the correct ratio.
Ignoring the change interval. Old coolant loses its corrosion inhibitors and becomes acidic, attacking the water pump, radiator, and heater matrix.
Assuming the same coolant applies to all models. AMG models and diesel engines may have different coolant specifications — check your owner's manual or use our Engine Code Guide to confirm.
Not flushing the system when changing coolant type. Residual old coolant can react with the new chemistry — always flush with distilled water before refilling. [EM-INTERVIEW]

How to Verify on the Actual Vehicle

The correct coolant type for your Mercedes is usually stamped on the coolant expansion tank cap, or listed in the owner's manual. You can also check the MB‑Approval number on the coolant bottle — genuine Mercedes coolant will display an approval number (e.g., 325.0, 325.3). To confirm your exact build specification, use our VIN Decoder tool — it will pull your vehicle's original coolant specification from the build data. For pre‑2005 models, a refractometer reading of 50% coolant concentration should indicate freeze protection around −37°C — if it reads lower, adjust concentration accordingly. [EM-INTERVIEW]

Why This Specification Matters

The correct coolant specification is not a minor detail — it is essential to the longevity of the cooling system and the engine itself. Using the wrong coolant can cause:

Corrosion — particularly in aluminium engine blocks and radiators, leading to pitting and eventual leakage.
Blockage — from sludge formation when incompatible coolants are mixed, reducing cooling efficiency and potentially causing overheating.
Water pump failure — incorrect coolant can degrade the water pump seal and impeller, leading to premature failure.
Overheating — if the coolant concentration is too low (e.g., too much water) or too high (e.g., too much coolant), heat transfer is reduced and the engine can overheat.

Mercedes cooling systems are designed for the specific chemistry of MB‑Approved coolants — deviations from the specification are a common cause of cooling system failures, which are expensive to repair. The cost of a coolant flush and refill with the correct fluid is negligible compared to the cost of a radiator, water pump, or head gasket replacement. See our Engine Overheating failure page for the consequences of ignoring this specification. [EM-INTERVIEW]

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Every Figure SourcedUnverified numbers are flagged, never guessed.

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Last Verified February 2026Reviewed on a regular schedule, not left to go stale.

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15+ Vetted Mercedes SpecialistsReal workshop insight behind the caveats, not just the spec sheet.

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100% IndependentNo sponsors, no manufacturer influence.

The Specification Table

Variant Differences

Notes & Caveats

Common Mistakes

How to Verify on the Actual Vehicle

Why This Specification Matters

Related Specifications

Coolant Specification →

Engine Code Decoder →

Engine Overheating Failure Page →

OM651 Oil Capacity →

M276 Oil Capacity →

VIN Decoder →

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