BMW Coolant Types — Can I Mix Them?

BMW has used different coolant colors over the years, and mixing the wrong types can cause problems. Here's the definitive guide.

BMW Coolant Specifications

BMW HT-12 (Current Standard)

• Color: Blue or blue-green
• Type: Hybrid Organic Acid Technology (HOAT)
• Used in: All BMWs from ~2018 onwards
• Lifespan: 4 years or 80,000 km

BMW LC-18 (Previous Standard)

• Color: Green
• Type: Organic Acid Technology (OAT)
• Used in: BMWs from ~2000-2018
• Lifespan: 4 years or 80,000 km

Older BMW Coolant

• Color: Blue
• Type: Inorganic Acid Technology (IAT)
• Used in: Pre-2000 BMWs

Can I Mix Them?

HT-12 + LC-18: Yes, but not ideal

They're compatible in an emergency, but mixing reduces the effectiveness of both. If you mix, flush and replace with a single type at the next service.

HT-12 or LC-18 + Generic Green/Orange: NO

Generic coolants (Prestone, Peak, etc.) may not be compatible with BMW's aluminum and magnesium engine components. They can cause:

• Corrosion of aluminum parts
• Gel formation (clogs the system)
• Seal degradation

Any Coolant + Water: Only distilled water

Never use tap water. Minerals in tap water cause scale buildup and corrosion.

The Safe Choice

Just use BMW-approved coolant. It's not expensive:

• BMW HT-12 concentrate: €15-25 per liter
• Zerex G-48 (equivalent): €10-15 per liter
• Pentosin Pentofrost NF (equivalent): €10-15 per liter

Mix 50/50 with distilled water. That's it. Don't overthink it.

When to Replace

• Every 2 years or 40,000 km (our recommendation)
• BMW says 4 years — that's the maximum, not the target
• Always replace after any cooling system repair
• If the coolant looks brown, rusty, or has particles — replace immediately