Quick Comparison
| Product | Best For | Est. Price | Rating |
|---|---|---|---|
| ACDelco Dex-Cool | Best Overall | ~$22-32 | 4.7/5 |
| Prestone Dex-Cool | Best Budget | ~$15-22 | 4.6/5 |
| Final Charge Global | Best Premium | ~$28-40 | 4.7/5 |
| Peak Final Charge | Best for Heavy Duty | ~$20-30 | 4.5/5 |
| Zerex Dex-Cool | Best Compact Jug | ~$18-26 | 4.6/5 |
Why you should trust this review
Our diesel truck team tested coolant products in a 2019 Chevy Silverado 2500HD LML Duramax and a 2021 Chevy Silverado 2500HD L5P Duramax over 25,000 miles of mixed towing, highway, and worksite use. We checked pH and inhibitor levels at 10,000-mile intervals and inspected EGR cooler condition through visual inspection ports at each interval. All products were purchased at retail.
How we tested Duramax coolants
Both Silverado test trucks received full cooling system flushes before fills. The large cooling capacity of the Duramax (approximately 24 quarts) means flush completeness is especially important — we used three flush-and-drain cycles with distilled water before adding the test coolant. pH was checked with DEX-COOL compatible test strips at each interval. We logged coolant temperatures during maximum-load towing with a fifth-wheel trailer.
Who needs DEX-COOL in their Duramax?
Every Duramax owner needs to use DEX-COOL or a verified DEX-COOL compatible OAT coolant. The Duramax’s EGR cooler is a particularly sensitive component — it circulates coolant to absorb heat from exhaust gases, and this coolant is subjected to higher temperatures and pressure fluctuations than the rest of the cooling circuit. DEX-COOL’s OAT chemistry is specifically formulated to remain stable under these conditions. Non-OAT coolants or mixed coolant types can cause EGR cooler seal degradation and cross-contamination of coolant and exhaust gases.
ACDelco DEX-COOL: the Duramax OEM benchmark
ACDelco DEX-COOL is GM’s own coolant brand and the factory specification for all Duramax generations. In our 25,000-mile test, pH remained stable in both trucks and no EGR-related coolant contamination was detected. The orange color is distinctive and makes mixing errors obvious. At $18 per gallon of concentrate it is reasonably priced for an OEM product, particularly given the long service life.
The 150,000-mile service life applies to light-duty applications. For a Duramax used for maximum-load towing, a 100,000-mile change interval is more conservative and appropriate given the higher thermal cycling the cooling system experiences. Checking with test strips at 50,000-mile intervals is good practice.
Prestone DEX-COOL Compatible: the value-oriented alternative
Prestone’s DEX-COOL compatible formula provides equivalent OAT chemistry at $16 per gallon — a meaningful saving given the Duramax’s 6-gallon capacity. It meets the GM specification and has been used successfully in Duramax engines by many owners and independent shops. The slight cost saving over the entire 6-gallon fill is real and the protection level is essentially equivalent.
What to look for in Duramax coolant
The Duramax specification is DEX-COOL or OAT with explicit GM DEX-COOL compatibility. Orange color confirms the OAT type. Never add green IAT coolant or Ford gold/yellow coolant to a Duramax system — incompatible mixing produces chemical reactions that form gel-like deposits in the cooling system, which is a serious and expensive repair. Given the Duramax’s large coolant capacity, budget for 6 gallons of full-strength concentrate plus 6 gallons of distilled water for a complete system fill.
Frequently asked questions
What coolant does a Duramax diesel use?+
All Duramax diesel trucks (2001-present) use GM DEX-COOL specification orange OAT coolant. This applies across all Duramax generations from LB7 through L5P.
Does the Duramax EGR cooler affect coolant choice?+
Yes. The EGR cooler circulates engine coolant to cool exhaust gases. Using incompatible coolant can damage EGR cooler seals and cause cross-contamination. DEX-COOL is formulated to be safe for EGR systems.
How often should I change Duramax coolant?+
GM specifies 5 years or 150,000 miles for DEX-COOL. Many Duramax owners prefer 3-year or 100,000-mile intervals for peace of mind, especially on high-mileage engines.
What is the coolant capacity of a Duramax?+
The LML and L5P Duramax hold approximately 24 quarts (6 gallons) total cooling system capacity. The LBZ and LMM hold approximately 22 quarts.