Valvoline.com

Cummins On Strong

Modern diesels—cleaner, quieter, more capable than before

Since the advent of the automotive age, diesel-powered vehicles have been considered by many to be noisy, dirty and underpowered. While Americans have viewed the diesel engine as the redheaded stepchild of the powertrain community and perceived diesel fuel as a "strange type of gas," Europe and Asia have long embraced diesel as a powerful and efficient fuel source. Here in the U.S., this alternative to gasoline has persevered by carving a popular niche among commercial trucking and weekend tow vehicles. Now, new developments in diesel engine technologies are creating cleaner, quieter choices for smaller cars, SUVs and luxury sedans without sacrificing performance.

Commercial haulers first turned their attention to diesels for their longer engine life—sometimes two-to-three times that of comparable gas-powered engines—and for their across-the-board superior ability to generate massive amounts of torque. What many may not know is that torque, as opposed to horsepower, is the force that propels a vehicle from a stop up to a comfortable cruising speed. Increased torque in a given vehicle results in faster acceleration and an increased ability to move large mass, i.e. tow heavy loads.

Break It Down

So how does a diesel engine work? Mechanically, diesel engines are very similar to gas engines. Both use a cylinder-enclosed piston that drives a crankshaft, which transfers power to a transmission and so on. And like gas engines, there are two primary types of diesels, two-stroke and four-stroke. Two-stroke engines are generally used for small or very large-scale machines, such as lawnmowers and cargo ships. Four-stroke designs are reserved for midsize machines requiring maximum fuel efficiency, such as automobiles.

So what makes a diesel engine different than a gas engine? The main difference is in the spark, or lack thereof, when it comes to diesel. In gas-powered engines, the fuel is fed into the cylinders and then ignited by a spark from a spark plug. Diesels, on the other hand, spray atomized fuel into the cylinder. As the piston stroke plunges upward, the mixture is compressed. This compression superheats the fuel-soaked air causing it to ignite and drive the piston downward creating energy. The result is a longer lasting, more efficient engine.

Keep It Quiet

Historically, another common byproduct of the diesel engine is increased noise and vibration, something that has kept would-be diesel fans reluctant to cross the powertrain fence. Enter the modern diesel engine. Today's diesels retain all of the long lasting, fuel efficient, high torque qualities they've become known for, while producing less noise and vibration than in years past.

A large reason for this improvement comes from the development of new injection systems that enable smoother operation. First unveiled in 1995, common rail direct injection (CRD) uses one pump to feed a primary fuel supply linked to the injectors. This system produces more power with less fuel, while making for a smoother, quieter running engine. Sophisticated electronic controls used in conjunction with CRD provide a wider powerband, smooth operation and less black smoke.

Cutting Costs

In addition to higher torque, passenger diesel-power cars can offer a nice financial benefit. Although the current cost of diesel fuel is comparable to that of premium unleaded, or about 10 percent higher than that of regular unleaded, some newer diesel-powered cars are capable of 30 percent more miles to the gallon—with comparable or better torque—to their gasoline counterparts. You do the math. And unlike the clumsy, slow and dirty diesels from the past, today's diesel engines are refined, responsive and emit dramatically reduced emissions.

Here we'll give you a basic rundown of the many diesel-powered vehicles available in the U.S. market today along with some of their benefits to you, the consumer.

Trucks

Dodge Ram 2500/2300: Powered by the Cummins Turbo Diesel, the Dodge Ram has set the standard for diesel power for decades. Proving its worth as a reliable powertrain, the Cummins engine offers truly impressive pulling power for drivers headed to the job site or the lake, or wherever our adventurous souls may take us.

In its current iteration, the 5.9-liter I-6 Cummins engine uses Chrysler's revolutionary CRD injection, a system that dramatically reduces engine noise and vibration. In the Ram, this diesel monster punches out 610 lb.-ft. of torque and 325 horsepower. Diesel power is an available option on all but one of the 2500 versions (gas only on the Power Wagon) and standard on all Ram 3500s.

Ford F-250/350 Super Duty: The Ford F-Series has been America's top selling truck for years with a proven track record for durability and performance. And Ford's Super Duty line of trucks continues that long-standing tradition with the signature 6.0-liter Power Stroke turbo diesel V-8 engine. Available as an option on all F-250s and F-350s, the Power Stroke delivers 570 lb.-ft. of torque and 325 hp.

Chevrolet Silverado 2500HD/3500 and GMC Sierra 2500HD/3500: Employing the same optional powertrains, Chevy and GMC's full-size pickups are motivated by the newly refined Duramax Diesel 6.6-liter V-8. Although less known than its Dodge and Ford competitors, GM has recently upped the ante with new engine tuning that raises power output to 650 lb.-ft. of torque and 360 hp, making it the segment leader in both categories.

Vans

Dodge Sprinter: Leading the way into the future is Dodge's Sprinter with its compact 2.7-liter I5 turbo diesel engine that delivers 243 lb.-ft. of torque and 154 hp. Like the Cummins powertrain in the Ram pickup, this lightweight package is also fueled by the CRD Injection system resulting in a smoother-running and much quieter diesel. The small displacement diesel is now standard equipment on all trims offering increased fuel economy and ample pulling power for even the heaviest loads.

Ford E-350: The Blue Oval's E-350 Super Duty is offered in several trims and configurations, however buyers opting for the 6.0-liter Power Stroke turbo diesel engine will find their choices slightly narrowed with the engine only available as an option on short wheelbased models. This de-tuned version of the F-250/350 powertrain produces 440 lb.-ft. of torque and 235 horsepower.

Chevrolet Express Work Van/GMC Savana Cargo: Available solely in 2500HD and 3500 models, Chevy Express and GMC Savana offer GM's Duramax 6.6-liter turbo diesel V-8 engine as optional equipment. Buyers of the optional diesel powperplant will enjoy 460 lb.-ft. of torque and 250 hp.

SUVs

Jeep Liberty: Breaking new ground in the compact SUV segment, the popular Jeep Liberty now includes a 2.8-liter turbo diesel as optional equipment on Sport and Limited trims. The stout engine generates an impressive 295 lb.-ft. of torque and 160 hp allowing V-8 towing capability in a small-sized SUV. Utilizing the same CRD Injection, the diesel-powered Liberty achieves an advertised 32 percent better fuel economy, which equates to almost 500 miles on one tank.

Looking for a Liberty CRD? You'd better act fast. Diesel, towing and general automobile enthusiasts alike have already caught on to this powerful compact hauler.

Hummer H1Alpha: Known the world over as the ultimate in off-road performance, the original Hummer derives its power from a diesel-propelled powerplant. At the heart of this machine, in both SUV and SUT iterations, is a new GM-built Duramax 6.6-liter turbo diesel that sports 520 lb.-ft. of torque and 300 hp. Although its diesel engine gives it extra pull when stuck in tight places, it's the Hummer's ability not to get stuck that gives it its longstanding title as king of the dirt.

Cars

Mercedes-Benz E320 CDI Sedan: Mercedes-Benz was once synonymous with diesel power in the U.S. Boasting an impressive 27 mpg in the city and 37 mpg on the highway Mercedes claims the E320 CDI can travel as far as 780 miles on one tank of diesel. Ensuring buyers receive comfort and performance that has become commensurate with the luxury brand, the 3.2-liter inline six enlists the Common-Rail Direction Injection to generate an astonishing 369 lb.-ft. of torque and 201 hp, which combine to propel the sedan from 0-60 in just 6.6 seconds.

Volkswagen Golf/Jetta/New Beetle: Like many European automakers, VW has been loyally producing diesel-powered cars for decades. Today in the U.S., the company that made "farfugnugen" famous offers a turbocharged direct injection 1.9-liter diesel in the Golf, Jetta and New Beetle. Available as an option on the Golf GLS and standard on TDI-version Jettas and New Beetles, the small displacement diesel yields 177 lb.-ft. of torque and 100 hp along with some head-turning EPA fuel economy estimates at 42 city and 49 highway for manual transmissions and 34 city 45 highway for automatic shifters (numbers vary slightly from model to model).