Showing specs for all NA & NB Miatas

Engine coolant type and antifreeze mixture (NB1)

Ethylene glycol-based coolant mixed with soft (demineralized) water; By volume: 35% coolant / 65% water for protection above −16°C (3°F); 45% / 55% above −26°C (−15°F); 55% / 45% above −40°C (−40°F). Do not use alcohol- or methanol-based coolant.
Factory manualTaken from a Mazda factory workshop manual, with page citation.
Procedure

Ratios are by volume and depend on required freeze protection. Do not use alcohol or methanol. Follow the cited year-specific filling, bleeding and level-check procedure; never open the cooling system hot. Specific-gravity figures differ in the 2005 table and are not combined into a universal target.

Applies to
  • NB 1999–2000 (BP-4W) — Other years in this family inferred from 1999 factory evidence with owner approval; actual-year verification is separate.
  • Verified in: 1999 Mazda MX-5 Miata Workshop Manual
Sources disagree. The factory manual value is shown; other published values are marked below.
Sources
  • 1999 Mazda MX-5 Miata Workshop ManualTier 1
    Page 01–12–2 (PDF p. 221)
    Ethylene glycol-based coolant mixed with soft (demineralized) water — differs
    Printed: “Use only ethylene-glycol-based coolant. Use only soft (demineralized) water in the coolant mixture.”
  • 1999 Mazda MX-5 Miata Workshop ManualTier 1
    Page 01–12–2 (PDF p. 221)
    Ethylene glycol-based coolant mixed with soft (demineralized) water; By volume: 35% coolant / 65% water for protection above −16°C (3°F); 45% / 55% above −26°C (−15°F); 55% / 45% above −40°C (−40°F). Do not use alcohol- or methanol-based coolant.
    Printed: “Antifreeze solution mixture percentage Coolant protection Volume percentage Water Coolant Gravity at 20°C {68°F} Above −16°C {3°F} 65 35 1.054 Above −26°C {−15°F} 55 45 1.066 Above −40°C {−40°F} 45 55 1.078”

Also in Additional factory manual gap audit