Engines
The era matters more than the badge
Every emissions tightening added hardware, and every piece of hardware added a way for the truck to stop. That is why a 2006 engine and a 2011 engine of the same displacement are different propositions entirely, and why pre-2007 trucks still command a premium two decades on.
So this reference is grouped by era rather than by manufacturer. It is the field that predicts your maintenance bill, and almost nobody tabulates it.
Pre-emissions
3 engines
Before exhaust gas recirculation. Mechanical or lightly electronic, no filter, no fluid, nothing in the exhaust to clog. They are old, they are dirty, and owner-operators still pay a premium for them for exactly one reason: there is far less on them that can strand you.
Cummins N14
14 LCummins · 1991 to 2000
A legend, and the last of the big mechanical-feeling Cummins engines before electronics took over completely. Celect and Celect Plus versions are electronically fuelled but have no exhaust hardware at all.
Detroit Series 60
14 LDetroit · 1987 to 2011
For a long stretch the best-selling heavy truck engine in North America, in 11.1, 12.7 and 14.0 litre forms. The 12.7 in pre-2004 trim is the one with the reputation, and it earned it: simple, economical for its era and enormously well supported.
Caterpillar 3406E
14.6 LCaterpillar · 1993 to 1999
Among the most admired truck engines ever built in North America, and the one people mean when they talk about old Cats. Electronically fuelled, mechanically simple everywhere else, and famously long-lived.
EGR (2004)
2 engines
Exhaust gas recirculation arrives: some exhaust is fed back into the intake to cut oxides of nitrogen. It raises cylinder pressure and heat, and it introduced the EGR cooler as a thing that fails.
Cummins ISX (EGR)
14.9 LCummins · 2002 to 2009
The engine that took Cummins through the first two tightenings, in dual-overhead-cam form. The pre-2007 version has no particulate filter, which is most of why those trucks still sell.
Caterpillar C15
15.2 LCaterpillar · 1999 to 2010
Caterpillar's last on-highway engine before it left the truck engine market in 2010 rather than build an SCR system. The pre-ACERT single turbo builds are the sought-after ones; the ACERT twin turbo builds are not.
DPF (2007)
1 engine
The diesel particulate filter arrives, and with it regeneration: the truck periodically burns off the soot it has caught. Regens cost fuel and time, and a filter that will not regen is a truck that will not move.
SCR (2010)
1 engine
Selective catalytic reduction adds a second fluid, diesel exhaust fluid, dosed into the exhaust to convert nitrogen oxides. It let manufacturers tune the engine for economy again, so SCR engines are generally BETTER on fuel than the DPF-only generation before them.
GHG17 (2017)
11 engines
The first greenhouse gas phase targets the whole vehicle rather than the engine, so this era is as much about aerodynamics, tyres and axle ratios as combustion. Downspeeding becomes standard: tall gears, low cruise revs.
Cummins X15
14.9 LCummins · 2017 to present
The volume choice in North American linehaul, sold in Efficiency and Performance series that are the same iron with different tuning and different ratings. Efficiency is aimed at fleets running tall gears at 62 to 65 mph; Performance is for heavy haul and hills.
Detroit DD15
14.8 LDetroit · 2008 to present
The fuel economy leader in most head-to-head fleet testing, particularly in the integrated Freightliner drivetrain with the DT12 automated transmission and a downsped rear axle. The amplified common rail fuel system is the technical differentiator.
Detroit DD13
12.8 LDetroit · 2008 to present
The lighter sibling, and around 400 pounds lighter than the DD15, which is payload on a weight-sensitive lane. Perfectly capable for linehaul under 80,000 pounds and noticeably thriftier.
Detroit DD16
15.6 LDetroit · 2008 to present
Detroit's heavy-haul engine, sharing architecture with the DD15 at greater displacement. Sold almost entirely into Western Star and severe-service Freightliners.
PACCAR MX-13
12.9 LPACCAR · 2010 to present
PACCAR's own engine, built on DAF architecture, and now the default in a large share of new Kenworths and Peterbilts. Compact graphite iron block, lighter than a 15 litre, and competitive on fuel with the Detroit.
PACCAR MX-11
10.8 LPACCAR · 2016 to present
Around 400 pounds lighter than the MX-13 and aimed at regional and weight-sensitive work. Enough engine for most linehaul that is not heavy or mountainous.
Volvo D13
12.8 LVolvo · 2007 to present
Volvo's mainstay, and with the I-Shift transmission and the turbo compound option one of the most fuel-efficient drivetrains sold. The integration between engine, gearbox and axle is Volvo's actual product.
Volvo D11
10.8 LVolvo · 2007 to present
The light option, around 400 pounds under the D13 and aimed squarely at regional work where payload is the constraint and the hills are not.
Volvo D16
16.1 LVolvo · 2007 to present
The heavy-haul option, and one of the largest displacement engines still offered on-highway. Bought for pulling rather than for economy, and it does not pretend otherwise.
Mack MP8
12.8 LMack · 2007 to present
Shares its architecture with the Volvo D13, Mack and Volvo being the same parent, with Mack calibration and the mDRIVE automated transmission. Strong in vocational and regional work.
International A26
12.4 LInternational · 2017 to present
Built on the MAN D26 block, and International's deliberate line under the MaxxForce era. Light for its output and well regarded on fuel.
18 engines. Displacement, horsepower and torque are manufacturer published figures. Fuel economy is a typical observed range for a loaded tractor, not an EPA number, because no EPA number exists for a drivetrain in isolation. Reliability notes describe failure modes these engines are known for in the field, not defect rates, which no manufacturer publishes.