Scoring Guide
How CarCareTruth Scores Coolant / Antifreeze
Last updated 2026-05-09
What We Measure — and Why It Matters
When buyers compare coolants, the first question is usually "will it hurt my engine?" — meaning: does it carry the right OEM approval for their specific vehicle? After that comes the health story, which for coolant is unusually important: ethylene glycol (the most common coolant base) has a documented sweet taste that attracts pets and children, with documented pet fatalities from accidental ingestion. Propylene glycol alternatives exist and are materially safer on that axis. The scoring system captures both the spec-compliance question and the safety chemistry question.
The Quality Score
Quality measures spec compliance first, because the wrong coolant for an OEM specification is not a quality product regardless of how well-marketed it is. The dominant dimension (40% of quality) is OEM approval: a coolant that carries named OEM endorsements (Honda, Toyota, GM, Ford, VW) on a publicly available TDS scores higher than one marketed as "compatible with all makes and models" without a cited spec number. After spec compliance, quality measures the protection range (freeze and boil points), the inhibitor technology and its documented service life (IAT coolants need changing every 2–3 years; OAT and HOAT systems claim 5+ years), and whether concentrate or pre-diluted options are available.
A coolant meeting outdated IAT spec with no OEM approvals is a below-average product even if it keeps a generic engine from freezing. The quality score is calibrated to that reality.
The Health Score
Coolant health scoring is built around one dominant concern: ingestion toxicity. Ethylene glycol (EG) is acutely toxic if swallowed — harmful at moderate doses, potentially fatal in larger ones, and its sweet taste makes it a documented hazard to pets and small children. Most standard EG coolants carry an H302 (harmful if swallowed) classification and land in the 7–9 range when handled according to label instructions by an adult. EG products with the more severe H300 classification (fatal if swallowed, Cat 1/2) are clamped to a 2.5 health ceiling — this is a fluid-specific override that reflects the severity of real-world ingestion incidents.
Propylene glycol (PG) coolants receive a +0.5 health bonus (capped at 9.5) because PG is materially less acutely toxic than EG — it's GRAS-listed for food use. This bonus only applies when the SDS confirms PG as the primary glycol base.
The handling exposure during a flush and fill — skin contact, incidental splash — is a secondary concern because EG vapor pressure at ambient temperatures is low. Still: gloves during drain work are reasonable for concentrate handling when H315 or H302 is present.
The health score reflects the SDS hazard classification and the realistic pour/handling scenario — not spec-compliance performance.
The Environment Score
Both EG and PG coolants are drain-destined at end-of-service and should be collected for recycling — not poured down storm drains or on the ground. Auto parts stores (AutoZone, O'Reilly, Advance Auto) accept used coolant. The environment score starts at 7.0, applies deductions for aquatic toxicity codes (H411 is common in EG formulas), multiplies by the drain-destined pathway factor (×1.25 for EG, ×1.10 for PG), and then applies biodegradability credits. Hard ceilings cap EG coolants at 4 and PG coolants at 5, reflecting the fact that glycol chemistry in runoff is a real ecological concern regardless of biodegradability. Scores of 3–5 are the expected range and correct — not a sign of an unusually harmful product.
The CCT Score
Quality 65%, Health 20%, Environment 15% (Stage 1) — then blended at 75% with a 25% CCT Opinion editorial score (Stage 2). Quality carries the most weight because spec compliance is the non-negotiable dimension: a coolant with the wrong OEM spec causes engine damage regardless of how safe it is to handle. Health carries a meaningful 20% share because EG vs. PG is a real buyer choice with real consequences — unlike most automotive fluid categories where all products have similar hazard profiles. Here, the gap between an EG product (health ~7.5) and a PG product (health ~9.0) is large enough to matter.
Concrete example: a standard EG HOAT coolant with quality 7.0, health 7.5, environment 4, and CCT Opinion 7.0 (null substitution). Stage 1: (7.0 × 0.65) + (7.5 × 0.20) + (4 × 0.15) = 4.55 + 1.50 + 0.60 = 6.65. Stage 2: 6.65 × 0.75 + 7.0 × 0.25 = 4.99 + 1.75 = 6.74 — a solid product, no badge. Add an OEM-approval upgrade (quality → 8.0) and a PG base (health → 9.0, env → 5) with a good opinion score (8.0): Stage 1: (8.0 × 0.65) + (9.0 × 0.20) + (5 × 0.15) = 5.20 + 1.80 + 0.75 = 7.75. Stage 2: 7.75 × 0.75 + 8.0 × 0.25 = 5.81 + 2.00 = 7.81 — Recommended.
What This Score Doesn't Measure
This score does not measure spec-compliance performance, drain-interval accuracy, or compatibility with named OEM specifications — those are quality-axis scores. Health is the SDS hazard classification translated for the realistic pour/handling scenario. The score does not test actual corrosion protection or freeze-point performance in a vehicle; those are determined by OEM and ASTM spec qualification testing, not community reviews. Scores reflect available SDS and TDS data plus community evidence — they are not the result of laboratory testing by CarCareTruth.