Kenworth T680 · fluids
Fluids & Fill AmountsHow much oil, coolant, DEF and gear oil this truck takes, and what specification to buy.
Set the year first
Then read the How much column as a refill quantity, not a dry fill. Fill to the dipstick or sight glass and treat the number as a starting point — a drain never gets everything out.
Fill amounts for Kenworth T680
| Fluid | How much | What to buy | Years | Source |
|---|---|---|---|---|
| Engine oil - PACCAR MX-13 (pan + new filters)Change it: Up to 75,000 mi line haul; 50,000 mi with >20% idle; 30,000 mi severe | 42 U.S. qt (40.0 L) | API CK-4 / FA-4, 10W-30 or 15W-40 | 2017–2026 | Verified |
| Engine oil - Cummins X15 (if fitted)Change it: 25,000-60,000 mi by duty cycle | 43.4 qt (41.1 L) steel pan / 45.4 qt (43.0 L) aluminum pan | API CK-4, CES 20086 | 2017–2026 | Verified |
| Engine coolantChange it: Test at PM | Approx. 13 gal (49 L) | OAT extended-life, min 15 psi pressure cap | 2017–2026 | Verified |
| Engine coolant (CARB aftertreatment config)Change it: - | Add 2.5 L to the base system | As above | 2017–2026 | Verified |
| Diesel exhaust fluid (DEF) tankChange it: Fill at every fuel stop | 7, 11, 21, 27 or 31 usable gallons by tank option | ISO 22241 DEF | 2013–2026 | Verified |
| Fuel tankChange it: - | 56-177 gal (24.5 in and 28.5 in round tanks) | ULSD, 15 ppm max | 2013–2026 | Verified |
| Transmission - PACCAR TX-12Change it: Not verified - consult OEM service manual | Not verified - consult OEM service manual | PACCAR-approved synthetic | 2017–2026 | Unconfirmed |
| Rear axle / differential (tandem)Change it: Not verified - consult OEM service manual | Not verified - consult OEM service manual | API GL-5 synthetic | 2013–2026 | Unconfirmed |
Sources: Cummins Quick Reference Guide 5410641 (X15 EPA 2017); Kenworth T680 product specification (February 2019); PACCAR MX-13 Operators Manual Y53-1100-1F1, Table 2; PACCAR MX-13 Operators Manual, Table 6; PACCAR MX-13 Operators Manual, Table 6 note 2
Two ways to wreck an engine in five minutes
Overfilling an oil pan aerates the oil and can damage bearings. Running a cooling system low can crack a liner or a head before the gauge even moves. Fill slowly, then check the dipstick or sight glass twice.