Diesel engines aren’t popular in America, except in trucks. This trend was accelerated after VW’s 2015 Dieselgate emissions scandal, relegating diesels to mainly heavy-duty and commercial applications, where they develop as much as 1,200 lb-ft of torque (the latest Ford 6.7L Power Stroke) and are ideal for hauling and towing with reasonable fuel economy.
Compiling a list of the most reliable diesel engines ever is a tough task and no single list is definitive. So, while we tried to rank the engines according to reliability, there isn’t a dud on this list and, despite a few problems to look out for that we mention, they should all last a long time with proper care. Many others could have made the list, too.
This list is not in strict order of reliability, as so many factors affect an engine’s lifespan. If it makes this list, it’s a good one. It’s a rough guide, also taking into account maintenance costs from RepairPal and data from CarComplaints. All of these were offered in cars and trucks sold in the US over the past 50 years or so.
10 BMW M57 3.0L I6
Years Made: 1998-2013
BMW
Engine Sizes
2.5L, 2.9L, 3.0L
Noteworthy Applications
3, 5, 6, 7 Series sedans and X3/X5 SUVs
Average Annual Repair & Maintenance Cost
$1,113 (2008 335d)
BMW’s M57 engine upheld BMW’s sporty image and delivered smooth performance and excellent reliability. These engines can run reliably for hundreds of thousands of miles with proper care, but the emissions equipment most often goes wrong, as is the case with most modern diesels. These parts need periodic replacement and issues can be deferred by taking the car on frequent highway runs, so the systems can get up to temperature quickly. But maintained properly, the hard points will last a long time.
Problems to be on the lookout for:
Leaks: turbo outlet hose, turbo oil line, and vacuum leaks Exhaust-gas recirculation (EGR) system failure Blocked diesel particulate filter (DPF) Harmonic balancer/crank damper failure Cooling system leaks and failed thermostats
9 Volvo Modular Engine D5 2.4L I5
Years Made: 2001-2010
Engine Sizes
2.0L, 2.4L
Noteworthy Applications
S60, V70, XC90
Average Annual Repair & Maintenance Cost
$644 (2007 V70)
When Volvo designed its Modular inline five-cylinder gas engine, it gave it a robust closed-deck aluminum block with iron cylinder liners capable of withstanding diesel combustion pressures. The diesel version followed later and it’s a tough lump. At least 200,000 to 250,000 miles should be expected from them, and more with meticulous maintenance. As usual, it’s mostly the hang-on bits that let go eventually, not the engine, though several of these issues could lead to engine failure. The timing belt is of a good design, but replace it at the set intervals, as a snapped one can ruin the engine.
Problems to be on the lookout for:
Bad engine cooling fans can cause overheating and engine failure Leaking fuel lines Oil consumption Timing belt failure
8 VW Group EA827 1.9/2.0 TDI
Years Made: 1989-2009 (1.9); 2003-present (2.0)
Engine Sizes
1.9L, 2.0L
Noteworthy Applications
VW Golf, Jetta, Passat, Audi A3, Q5
Average Annual Repair & Maintenance Cost
$630 (Golf 1.9) $1,058 (Q5 2.0)
The iron-block 1.9-liter TDI had two valves per cylinder and was noisy and unrefined, but it was tough. Big mileages are possible with routine maintenance, and fuel consumption is superb. The 2.0-liter engine used the 1.9 design as a base (both are part of VW’s expansive EA827 engine family), but with a larger capacity and 16 valves, and was used in cars such as the Audi A3. The basic design is extremely durable, but the emissions equipment can fail – a common theme in this article. These engines use a timing belt that must be replaced at the prescribed intervals.
Problems to be on the lookout for:
EGR failure Dual-mass flywheel (DMF) failure on manual cars Timing belt failure Oil leaks, especially the valve cover
7 Ram HD 5.9/6.7L Cummins ISB I6
Years Made: 1998-2006 (5.9); 2007-present (6.7)
Engine Sizes
5.9L, 6.7L
Noteworthy Applications
Ram HD
Average Annual Repair & Maintenance Cost
$1,279 (Ram 3500 HD)
The Cummins inline six-cylinder in the Ram HD trucks is torque-rich and durable. It can trace its roots back to 1984, when the first Cummins B Series launched and used cylinder bores machined into the block from the start, not wet liners. The ISB used from late 1998 succeeded the 6BT and is an unusual 24-valve pushrod design. Both 5.9L ran until 2006 and the 6.7L took over from there. They are extremely robust and reliable, capable of an easy 300,000 to 350,000 miles or more with proper care. The issues are mostly associated with the emissions equipment.
Problems to be on the lookout for:
VP44 diesel injection pump failure (1998.5-2002 5.9L) Clogged DPF (worse on pre-SCR pre-2013 models) EGR cooler failure Sticking VGT turbo vanes (pre-2010)
6 Ford Super Duty 6.7L Power Stroke V8
Years Made: 2011-present
Engine Sizes
6.7L
Noteworthy Applications
Ford Super Duty F-250, F-350
Average Annual Repair & Maintenance Cost
$1,295 (F-350)
From 2011, Ford fielded its own in-house 6.7L turbo-diesel V8 for HD trucks like the Ford F-250 Super Duty. It’s a first-rate effort in a make-or-break class. Earlier turbos with ceramic ball bearings failed, but were soon upgraded, along with a six-bolt bolt pattern per cylinder, which reduced the likelihood of gasket failure. The Bosch fuel-injection pump on early models was also unreliable. These issues were sorted out by 2015. This robust engine is still used today with as much as 500 hp and 1,200 lb-ft of torque and is durable and powerful, capable of hundreds of thousands of miles if properly maintained.
Problems to be on the lookout for:
Ceramic ball-bearing failure on 2011 and 2012 turbochargers Head-gasket failure on early models Pre-2015 Bosch CP4.2 injection-pump failure Stuck EGR valve and EGR cooler failure
5 Toyota 1HD-FTE 4.2L I6
Years Made: 1998-2007
Engine Sizes
4.2L
Noteworthy Applications
Hilux, Land Cruiser
Average Annual Repair & Maintenance Cost
$805 (2007 Land Cruiser)
It might have packed only 164 hp at launch, but the 1HD is a bullet-proof engine capable of huge mileages. Available in other parts of the world without a turbocharger and around 130 hp, this versatile engine cannot be killed as long as you stick to routine maintenance. Just remember to replace the timing belt on time. Most of the issues again have to do with emissions systems, and not the engine itself.
Problems to be on the lookout for:
Clogging of EGR and intake Timing belt failure Valve clearances to be adjusted every 40k miles Injection pump and injector issues
4 Chevrolet HD 6.6L Duramax LB7/LBZ V8
Years Made: 2001-2004 (LB7); 2006-2007 (LBZ)
Chevrolet
Engine Sizes
6.6L
Noteworthy Applications
Chevy Silverado, GMC Sierra
Average Annual Repair & Maintenance Cost
$883 (2012 GMC Sierra 2500 HD)
GM developed the LB7 6.6L Duramax in collaboration with Isuzu – a modern turbocharged and intercooled V8 with four valves per cylinder, Bosch common-rail diesel injection, and aluminum cylinder heads for use in Chevy Silverado and GMC Sierra trucks. The injection system caused a few initial headaches that were soon fixed. Forged steel internals (crank and cap rods) and simple iron cylinder liners improve durability. This durable engine is commonly seen exceeding 500,000 miles. The subsequent LBZ version received a stronger block, bores with more depth, and stronger rods and main-bearing caps. Unbound by costly emissions equipment, it was extremely reliable.
Problems to be on the lookout for:
Injector problems (LB7) Fuel-filter housing O-ring leaks (LB7) Water-pump failure (LB7 & LBZ) EGR valve failure (LBZ)
3 International Navistar T444E 7.3L Ford Power Stroke V8
Years Made: 1994-2004
Wikipedia
Engine Sizes
7.3L
Noteworthy Applications
Ford Super Duty F-250, F-350
Average Annual Repair & Maintenance Cost
$1,295 (F-350)
Supplied by International Navistar, the first Power Stroke V8 wasn’t a Ford design, but the T444E V8 from International Navistar Novel features included Caterpillar-designed hydraulically actuated and electronically controlled HEUI injector tech. Forged internals arrived in 2000 and the all-iron pushrod V8 was virtually bullet-proof, while hydraulic lifters reduced maintenance. It will go for 500,000 miles or more, and even those nifty injectors don’t require attention before 200,000 miles at the very earliest. The most reliable ones were built after 1997.
Problems to be on the lookout for:
Camshaft-position sensor failure Turbocharger up-pipe can leak Failure of injector-pressure regulator Fuel-filter housing leaks
2 Mercedes-Benz OM601 I4 / OM602 I5 / OM603 I6
Years Made: 1983-2000
Mercedes-Benz
Engine Sizes
2.0L, 2.2L, 2.3L I4; 2.5L, 2.9L I5; 3.0L, 3.4L I6
Noteworthy Applications
W124
Average Annual Repair & Maintenance Cost
N/A
This more advanced engine succeeded the superbly reliable OM616/OM617. It was a modular engine, with four (OM601), five (OM602), or six (OM603) cylinders in line, continuing the reputation of reliability forged by the OM617, and many of these have exceeded a million miles. So durable is this engine family, that it seems by many pundits to be the only one approaching the famous OM616/OM617 for pure staying power.
Problems to be on the lookout for:
Uneven idling Cracked cylinder heads (early OM60397 only) Bent rods (early OM60397 only)
1 Mercedes-Benz OM616 I4 / OM617 I5
Years Made: 1974-1991
Mercedes-Benz
Engine Sizes
2.0L, 2.4L I4, 3.0L I5
Noteworthy Applications
W123, W116
Average Annual Repair & Maintenance Cost
N/A
Often touted as the most reliable engine ever made, Dr Ferdinand Piëch, the man behind Audi’s five-cylinder engine and quattro drivetrain, designed the modular OM616/617 engines while at Mercedes-Benz. These engines seem to run to 500,000 miles with regular maintenance, as a matter of course, and there are examples that have racked up millions. The 3.0L was equipped with a turbocharged later on and became the first turbo-diesel engine ever sold in the US, in the W116 generation 1978 Mercedes 300SD. It had only 115 hp, but it retained its reputation for reliability. The highest mileage ever recorded on one of these engines is a 2.4-liter four-cylinder W123 taxi in Spain that has racked up more than 4.3 million miles.
Problems to be on the lookout for:
These engines are now so old. Check everything, as the mileages are now huge and any of a list of problems could be present due to age.
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Sources:
Slashgear,
CarComplaints
,
RepairPal
,
MotorTrend
,
HotCars
, DieselWorld,
CarSurvey
.