Diesel Buying Guide

Because it uses compression to ignite the fuel rather than a spark, a diesel engine is better at converting kinetic energy into mechanical energy. What that means for you is more miles per gallon than with a comparable gas engine — on average, diesel engines get 25-35% better fuel efficiency. That's why, if you choose a 2014-2018 BMW X5 35d powered by a diesel engine, you get EPA-estimated 29 mpg on the highway.

• Long-cruising mileage for road trips

• Fewer pit stops for fuel

• Better estimated MPG in larger vehicles

• More time commuting between fill-ups

• Lower total cost of ownership

While diesel engines may lag behind in horsepower, their advantage is low-end torque. Torque is important for acceleration and is essential for any towing or hauling. Because of that high compression, diesel engines have lots of torque, and you don’t have to wait for high engine revs to get it. That means medium-duty diesel engines are ideal for towing anything from weekend toys to worksite trailers. For example, the 3.0L six-cylinder turbodiesel in the 2020-2022 Ram 1500 2x4 can tow up to an estimated 8,290 pounds when properly equipped.

• Fewer downshifts when highway cruising

• Better acceleration under load

• Improved fuel mileage when towing

• More towing capacity out of a smaller engine displacement

• Stronger crawl when off-roading.

Diesel engines are designed with fewer moving parts than a gasoline engine. They’re typically much less complex, as well. Fewer moving parts means there's less to go wrong over the life of an engine. Diesel engines often last longer because they are designed to withstand the higher compression forces. They are typically built using heavier-duty materials and thicker metal. The diesel engine in a 2018-2019 Chevrolet Equinox may be why it earns an above-average 4/5 RepairPal reliability score.

• Lower total cost of ownership

• More life out of your vehicle

• Fewer parts to replace

• Less time at the shop

• Potentially higher reliability

Diesel engines don’t use many of the parts a gas engine does, like spark plugs. In addition to lasting longer, a diesel engine requires fewer regular maintenance items. That doesn’t mean there is no maintenance to perform, however. Like any other engine, the best way to get the most out of a diesel engine is to keep up with regular checks and servicing. Maintenance is an essential part of owning any vehicle. Having less to maintain means:

• Fewer trips to the mechanic

• Easier to follow maintenance schedule

• Lower overall cost of ownership

• Fewer parts than a gasoline engine

• Potentially DIY friendly

When choosing a diesel car, it’s important to consider how it fits into your lifestyle. If you have a long highway commute, for example, a diesel car is ideal as it'll likely go easier on fuel than a gasoline version. For towing recreational vehicles, the low-end torque of a diesel engine handles loads with ease. You can still get the precise handling and thrilling driving dynamics of a sports sedan with a diesel-powered car.

• Diesel engines are great for towing and off-roading

• Add the efficiency of a diesel engine to your daily commute

• Even sports sedans can use diesel engines

In most cases, a diesel engine is available as an option on mid- to high-end trims. Their lower maintenance intervals can offset a higher purchase cost, and a diesel engine may last longer, giving you more life from a diesel vehicle. Mileage doesn’t always tell the story, however, because a poorly maintained low-mileage car can have more issues than a higher mileage car that’s well maintained.

• Diesel engines are typically in a higher budget range

• A well-maintained diesel engine has lots of life, even with some miles on it

• Diesel engines may have a lower cost of ownership

One of the key things to look for in a diesel engine is torque values. If you’re towing or going off-road, lower-end torque is important. Check at which RPM the diesel engine gets its peak torque, often much lower than a similar gas engine. In some cars, like the BMW 328, the diesel engine trim gets its own model designation, the 328d. Other things to compare:

• Automatic or manual transmission

• Trim features to get the options you want

• EPA-estimated combined mpg numbers

The Jeep Grand Cherokee makes a great family SUV, with lots of comfort features and a spacious cabin. The Jeep Wrangler, on the other hand, is better suited for enthusiast-level off-roading, boasting a rugged body-on-frame design and an available suite of off-road equipment. Read more about how these two SUVs stack up on our comparison tool.

Jeep Grand Cherokee Advantages

• Excellent infotainment system with smartphone integration

• Plenty of room for passengers and their cargo

• Available driver-assist features

Jeep Wrangler Advantages

• Impressive off-road capability

• Removable windows, doors, and roof panels for an open-air ride

• Available smartphone connectivity

Offering variations of a luxury sedan, the BMW 328 and the Jaguar XE give you the choice between luxurious comfort and stylish sport. The Jaguar XE leans toward comfort and luxury, but still has a spirited side, while the high-tech, sporty BMW 328 will bring a smile to your face. Head over to our comparison tool and read more about these two sport luxury sedans.

BMW 328 Advantages

• Blend of performance and refinement

• Powered by a 3.0L six-cylinder diesel engine (328d models)

• Available suite of modern tech

Jaguar XE Advantages

• Performance-tuned diesel engine option

• Luxurious interior

• Standard 10-inch touchscreen with smartphone integration

Both of these capable pickup trucks are excellent choices for anyone with mid- or heavy-duty hauling needs. The Ram 1500 is better suited for mid-duty work, but has a more refined ride and plenty of creature comforts. A Ram 2500, however, blends the heavy-duty punch of a Cummins® diesel with an impressive list of available features. You can see more side-by-side information on these Ram models using our comparison tool.

Ram 2500 Advantages

• Up to an estimated 19,900 pounds of towing capacity

• Available 6.7L six-cylinder Cummins diesel engine

• Available suite of driver aids, including towing tech

Ram 1500 Advantages

• Unique all-around coil spring suspension for a softer ride

• Available luxury features like real wood trim and air suspension

• Available 14.4-inch touchscreen

One is a heavy-duty hauling machine, while the other is a capable mid-duty truck, but both feature available diesel engines. Both the Ford F250 and the GMC Sierra 1500 offer impressive towing and driver-assist technology, available luxury packages, and loads of practicality. However, the F250 excels at heavy-duty tasks, while the Sierra 1500’s more composed ride makes it better for around-town driving. More details are available in our comparison tool.

Ford F250 Advantages

• Available towing technology

• Capable of hauling impressive numbers

• Comfortable seating and a spacious passenger cabin

GMC Sierra 1500 Advantages

• Lots of available driving aids

• Available towing equipment and technology

• Available 3.0L six-cylinder diesel engine that delivers smooth power

If you’re looking for a practical truck with good towing capability for everyday life, the Ford F150 is an ideal pick. Or, if you need something heavy-duty to tackle life’s biggest jobs, take a look at the GMC Sierra 2500. Both trucks combine the power of a diesel engine, towing technology, and a range of creature comforts. Dig deeper into these two trucks by using our comparison tool to see them side-by-side.

Ford F150 Advantages

• Available with a 3.0L diesel engine (2018-2021)

• Impressive suite of available towing technology

• The King Ranch and Platinum trims rival luxury sedans

GMC Sierra 2500 Advantages

• Spacious passenger cabin with a range of comfort options

• Available driver assists and towing technology

• A selection of powerful engines, including a 6.6L diesel engine

The Mercedes-Benz E250 and E350 are both members of the E-class family. The E250 trim is available for 2014-2016 model years, while the diesel E350 is available for 2013 and earlier models. Both cars exude luxury, are packed with features, and have confident handling. You can use our comparison tool to see how these two cars stack up.

Mercedes-Benz E250 Advantages

• The available AWD provides added confidence in poor driving conditions

• Satellite radio and some driver assists are available through tech packages

• Plenty of standard features

Mercedes-Benz E350 Advantages

• Available with either a gas or diesel engine (2013 and earlier)

• Impressive list of comfort and technology features

• Comfortable seating throughout, complemented by a refined ride

Direct injection is a common fuel-injection system found in both gas and diesel engines. Direct injection, as the name suggests, injects fuel directly into the cylinder. Direct injection has many advantages, including better efficiency, lower emissions, and lower vibrations than indirect injection engines.

Indirect injection diesel engines initiate fuel combustion outside the cylinder, often in a small area called a swirl chamber. The expanding gases force the fuel from the side chamber into the cylinder, where most of the power is generated. A glow plug, or heating element, is often used to warm the fuel and air to the ignition point.

Building on the idea of direct injection, a common-rail system uses a single fuel line, pressurized by the fuel pump, to feed the injectors in the engine. This system separates fuel injection timing and pressure, allowing an electronic controller to fine-tune injection timing. A CRDI engine gives engineers more control over efficiency, power, and emissions.