Buyer Research

2020 Peterbilt 579 PACCAR MX-13 — Should You Buy One?

Typical asking price: $80,000–$115,000. There are 2 high-severity known issues you need to know before handing over a check.

Kestrel Take

The 579 is Peterbilt's aerodynamic flagship — fuel-efficient, driver-friendly, and equipped with Peterbilt's SmartNav and optional Bendix ADAS. The MX-13 by 2020 is a mature engine with most early issues resolved. Solid choice for a used long-haul truck with modern features.

Known Issues for the 2020 Peterbilt 579 PACCAR MX-13

Ranked by wallet impact. These are documented, recurring problems — not freak accidents.

MX-13 aftertreatment systemHigh — wallet impact

DEF, DPF, and SCR system failures trigger derate modes. Pre-purchase ECM scan is mandatory.

Repair cost range: $500-$4,000

MX-13 EGR coolerHigh — wallet impact

EGR cooler failures on the MX-13 — white smoke and coolant loss are the indicators. By 2020 the cooler design had improved but not eliminated the concern.

Repair cost range: $2,000-$5,000

ADAS radar and camera calibrationMedium

Bendix Fusion or OnGuard ADAS requires calibration after windshield replacement. Verify all safety systems active.

Repair cost range: $500-$1,500 to calibrate

Walk-Away Red Flags

✗Active emissions or engine fault codes on ECM scan
✗White smoke or coolant loss — EGR cooler
✗ADAS warning lights active

Good Signs

✓Peterbilt dealer PM service history
✓ECM scan clean
✓Long-haul highway miles
✓EGR cooler replaced or inspected and documented

Found a specific Peterbilt 579 PACCAR MX-13?

This page covers what goes wrong on the 2020 Peterbilt 579 PACCAR MX-13 in general. The Kestrel report covers this specific car— the asking price vs. market, the photos, the seller's description, and a BUY / NEGOTIATE / WALK AWAY verdict with a negotiation script.

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Known issues on this page are based on documented owner reports, NHTSA complaints, class-action records, and manufacturer technical service bulletins. Individual vehicles vary. A pre-purchase inspection by a trusted mechanic is always worth doing.