15W-40 Heavy Duty Diesel Oil, 1 Gallon (3.78L), API CK-4 Certified. 15W-40 is the long-standing standard for diesel pickup trucks — Ram Cummins, Ford Power Stroke, and GM Duramax all commonly specify this grade for conventional or synthetic-blend service. Apex Auto Spare Parts stocks CK-4 certified 15W-40 ready to ship across Canada and the US.
Quick Specs (Heavy Duty Diesel Engine Oil 15W-40 — 1 Gallon — Cummins, Power Stroke, Duramax)
| Viscosity Grade | 15W-40 |
| Type | Conventional / Synthetic Blend (heavy duty diesel) |
| API Certification | CK-4 — backward compatible with CJ-4, CI-4 |
| Container Size | 1 US Gallon (3.78 Litres) |
| Recommended Interval | 8,000–16,000 km depending on use — severe duty (towing) shortens interval |
Common Applications
- Ram 2500/3500 — 6.7L Cummins, 5.9L Cummins
- Ford F-250/F-350/F-450 — 6.7L, 6.4L, 6.0L Power Stroke
- Chevy/GMC 2500HD/3500HD — 6.6L Duramax
- Most pre-2017 diesel pickups specify 15W-40 as standard
⚠️ CK-4 vs FA-4: Newer diesel engines (2017+) may specify the thinner FA-4 oils for fuel economy. CK-4 is backward compatible with older specs (CJ-4, CI-4) but check your owner’s manual if your truck is 2017 or newer — it may call for FA-4 specifically.
Why CK-4 Matters
- CK-4 oils offer improved oxidation resistance and shear stability over older CJ-4 specs
- Better protection against oil aeration — important for high-pressure common-rail diesel injection systems
- Backward compatible — safe to use in older diesel engines that specified CJ-4 or CI-4
Severe Service Considerations (Heavy Duty Diesel Engine Oil 15W-40 — 1 Gallon — Cummins, Power Stroke, Duramax)
- Frequent towing, hauling, or extended idling shortens recommended oil change intervals — follow severe duty schedule
- Diesel oil darkens faster than gasoline engine oil due to soot loading — this is normal and doesn’t necessarily mean immediate change is needed
- Always check oil level and condition before long trips, especially in winter
Not sure which oil your engine needs?
Call or WhatsApp us with your year, make, model & engine — we confirm the correct viscosity and spec before you order.
📞 +1 (512) 236-5489 💬 WhatsAppQuestion:
- What oil viscosity does my Cummins, Power Stroke, or Duramax need?
- Should I use 15W-40 or 5W-40 in cold weather?
- What’s the difference between API CK-4 and CJ-4 diesel oil?
- Is full synthetic diesel oil worth the extra cost?
- Can I use 15W-40 in a newer diesel truck with a DPF?
- How often should I change the oil in a diesel truck?
- Does Cummins recommend a specific oil brand or just a spec?
- Is store-brand 15W-40 as good as premium brands like Rotella or Amsoil?
- What oil capacity does a 6.7L Cummins or 6.6L Duramax take?
- Can I switch between 15W-40 and 5W-40 with the seasons?
