Detroit (Daimler Truck)
Detroit DD15: Specs, Service Intervals, Lifespan & Common Problems
The Detroit DD15 is a 14.8-liter inline-six diesel. It is the standard heavy-duty engine in most Freightliner Cascadias. Detroit lists the DD15 family at 425–505 hp and 1,550–1,850 lb-ft. The on-highway Gen 5 spec sheet covers 425–475 hp and 1,550–1,750 lb-ft. Detroit's service intervals run from 35,000 miles for severe duty to 75,000 miles for efficient long-haul. Its standard warranty covers major components through 500,000 miles.
Figures taken from the manufacturer's own published documents. Last reviewed September 23, 2026.
What are the Detroit DD15 specs?
| Configuration | Inline 6-cylinder |
|---|---|
| Displacement | 14.8 L (906 cu in) |
| Bore × stroke | 5.47 in × 6.42 in (139 mm × 163 mm) |
| Compression ratio | 21.0:1 |
| Power and torque (DD15 family) | 425–505 hp, 1,550–1,850 lb-ft per Detroit's engine page |
| Power and torque (Gen 5 on-highway sheet) | 425–475 hp, 1,550–1,750 lb-ft |
| Dry weight | 2,718 lb (1,233 kg) |
| Oil and filter service fill | 45 qt (43 L) |
Commonly paired with the DT12; see the transmission specs reference.
Fitted in the Freightliner Cascadia; compare with the truck model specs.
How long does a Detroit DD15 last?
The Gen 5 on-highway spec sheet doesn't state a B10 or B50 design-life figure, so this page doesn't either. Figures you see quoted elsewhere aren't from the sheet we reviewed. What Detroit does publish is warranty terms. The standard warranty extends to major components from month 25 through month 60 or 500,000 miles, whichever comes first. It covers parts but not labor. That's the OEM's actual commitment. It's the number to compare against other makers' written terms.
Warranty, as the OEM lists it
- Major components: months 25–60 or up to 500,000 miles (800,000 km), whichever comes first
- In that extended period, parts are covered at no charge; labor is not covered
How often should you change the oil in a Detroit DD15?
Detroit's Gen 5 on-highway intervals below assume Detroit's fluid specification 93K222 (CK-4) or 93K223 (FA-4) approved oils. They are recommended when using Detroit lube oil with its oil analysis program. Miles or hours apply, whichever comes first.
| Duty cycle | Oil and filter interval |
|---|---|
| Severe duty (up to 30,000 annual miles, under 5 mpg) | 35,000 miles or 750 hours |
| Short-haul (30,000–60,000 annual miles, 5.1–5.9 mpg) | 45,000 miles or 1,000 hours |
| Long-haul (over 60,000 annual miles, 6.0–6.9 mpg) | 60,000 miles |
| Efficient long-haul (over 60,000 annual miles, over 7 mpg) | 75,000 miles |
- The oil-and-filter and fuel-filter intervals are the same on this sheet for each duty cycle.
- DEF pump filter: replace every 3 years or 500,000 miles (800,000 km), whichever comes first.
- Your real interval depends on your duty cycle, not the trailer you pull. A truck that idles a lot or runs low mpg belongs in a shorter category.
Put your interval on a schedule with the maintenance scheduler.
What are the common problems with the Detroit DD15?
For the DD15, repair-industry sources most often point to three areas.
- EGR cooler
- Reports of EGR cooler failures center on older DD15 generations. Repair-industry sources place them at roughly 400,000–600,000 miles. A failing cooler can show up as coolant loss and white smoke.
- Variable-geometry turbo actuator
- The VGT actuator is a frequently reported wear item. Symptoms include poor acceleration, black smoke, and fault codes tied to boost control.
- Aftertreatment and DEF system
- DEF and aftertreatment faults are the most commonly reported source of derates on any modern Detroit. They are typically the most expensive category when they do need repair.
There is no public, independent failure-rate data for any heavy-duty diesel. So this section isn't a defect ranking. It lists the repair categories that shops and parts suppliers repeatedly report for this engine. Those sources sell repairs and parts, which is worth remembering. The same handful of systems (EGR, turbo, aftertreatment, fuel system) show up on every modern SCR-equipped diesel. Treat these as things to inspect on a used truck and to watch on your own, not as odds.
When a warning light comes on, decode it with the fault code lookup. Before you buy a used truck, run the VIN decoder and the used truck inspection checklist.
How does it compare with other heavy-duty engines?
Each engine guide on this site follows the same format and the same sourcing rule, so you can read them side by side.
Frequently Asked Questions
How long does a DD15 engine last?+
Detroit's Gen 5 spec sheet doesn't publish a design-life mileage. So any specific number you see online isn't coming from Detroit's own sheet. What Detroit does commit to in writing is major-component warranty coverage through 500,000 miles. Repair-industry sources commonly describe well-maintained DD15s running well past that. But no independent study backs a specific figure. How long yours lasts depends far more on following the right service interval for your duty cycle than on the engine model.
What are the common problems with the DD15?+
The categories repair shops report most are the EGR cooler, the variable-geometry turbo actuator, and aftertreatment/DEF faults. These come from repair and parts businesses, not an independent failure study. So read them as areas to inspect on a used truck, not as failure rates. Note that the same categories show up on virtually every modern SCR-equipped diesel.
How often should I change the oil in a DD15?+
Detroit's Gen 5 on-highway sheet lists these oil intervals. Severe duty: 35,000 miles. Short-haul: 45,000. Long-haul: 60,000. Efficient long-haul (over 7 mpg): 75,000. They assume approved CK-4 or FA-4 oil. Match your interval to your real yearly miles and mpg, not to the biggest number on the chart.
Is the DD15 a good engine?+
It's the most widely installed heavy-duty engine in the Cascadia. That is why parts and trained technicians are easy to find almost anywhere. That availability is a practical advantage, apart from any reliability claim. As with every engine here, the result for a given truck comes down to maintenance history. So a documented service record matters more than the badge.
Sources
Want a dispatcher to handle this for you?
Grow Trucking finds loads, negotiates rates and does the paperwork for owner-operators and small fleets. Tell us about your truck and we will show you how we can help.
Also: About Grow Trucking · Refer a carrier · Trucking blog
Specs, intervals and warranty terms change by model year and configuration. Confirm the exact figures for a specific truck against the maker's current documents and your written warranty before you make a purchase or maintenance decision. Reported-issue information comes from repair and parts businesses, not from an independent failure study.
Free tools for a Detroit DD15 truck
Decode fault codes, keep service on schedule and check a truck before you buy.
- Diesel Fault Code Lookup (SPN/FMI)Decode the SPN/FMI fault codes this engine reports.
- Preventive Maintenance SchedulerTrack oil and filter intervals by odometer for your duty cycle.
- Breakdown Cost EstimatorEstimate what a breakdown costs in repairs and lost revenue.
- Truck Breakdown TriageIf this engine shows a red lamp or overheats, see if you should stop now.