Aside from the smoke, and the smell, and the clatter, and the hard starting in winter, the traditional objection to diesel engines was cost.
Compared to a similar gasoline engine, diesels often cost thousands of dollars extra, so prospective owners were obliged to do sums with their golf pencils to figure out if the diesel's better fuel economy was worth it.
Most of the complaints eventually vanished by the waysides. Modern oil burners are indistinguishable from their gasoline counterparts. They start instantly in any weather, are funeral home quiet and the only detectable odor is from the pump at the filling station.
Now Mercedes-Benz has even mitigated the cost objection with the 2013 GLK 250 diesel compact sport utility vehicle -- at least if you compare it with its gasoline-engine sibling, the GLK 350.
The 350 with standard rear-wheel drive carries a base price of $37,995, including the $905 destination charge. If you add the 4Matic all-wheel drive, the price tag is $39,995. The diesel 250 has a sticker of $39,495, though you can spend north of $57,000 with options.
That means that the diesel, which comes standard with all-wheel drive, is priced just $1,500 more than the base GLK 350. For that amount, the buyer gets both the diesel engine and all-wheel drive. Even more intriguing, the diesel actually is priced at $500 less than the gasoline GLK 350 with all-wheel drive.
With a 302-horspower, 3.5-liter V6 engine, the gasoline 350 is quicker off the line. Mercedes-Benz lists the zero to 60 miles an hour acceleration time at 6.4 seconds.
Yet it would be difficult to argue that it's a better overall performer than the 200-horsepower four-cylinder diesel, despite the diesel's zero to 60 rating of 7.9 seconds. Both restyled GLKs use a seven-speed automatic transmission.
The equalizer is torque, or twisting force. The diesel is rated at 369 pounds-feet compared to the gasoline-engine's 273 pounds-feet. Twin turbochargers contribute to the 250's hefty torque, which delivers a jump off the line that makes the diesel feel faster than it is. However, the torque advantage dissipates at highway speeds, where passing is leisurely.
The 250's electric power steering and suspension system are biased toward precise handling, which results in a choppy ride. There's some under-steer, so you must hold the line in curves against a tendency to move straight ahead. Front seats are flat with little lateral support.
On fuel economy, the diesel 250 smokes the 350. The EPA rates the 250's city/highway/combined mpg at 24/33/28 mpg, compared to 19/24/21 for the 350. Mercedes says that gives the 250 an effective range of more than 500 miles.
Its economy advantage is mitigated somewhat by the design of the 2.1-liter 250 engine, which uses extra-cost urea injection to reduce pollutants. Mercedes calls the fluid BlueTec. It resides in a 7.3-gallon tank under the rear cargo floor that must be topped up periodically.
Mercedes was the first manufacturer to market a diesel passenger car in 1936, and brought its first diesel to the United States in 1949. By 1982, eight in ten Mercedes cars were powered by diesel engines.
The new diesel is the first with four cylinders from Mercedes in about a quarter of a century. During that time, the company's diesels had four, five or six cylinders in line or in a V configuration. With recent huge advances in power from small gasoline engines, diesels also have improved so that four cylinders now suffice.
Given its entry-level luxury orientation, the GLK has a relatively low price of less than $40,000. However, there's a long list of options that customers typically order. The tested GLK started at $39,495 and, with options that included a panoramic sunroof, auto-dimming mirrors, satellite radio, the Mercedes COMAND system with navigation, rear-view camera, heated front seats and a styling package from Mercedes's AMG performance division, it had a bottom-line sticker price of $50,735.
That included the MB-Tex upholstery, which is a high-quality vinyl that resembles leather. However, if you want real leather, it will set you back an additional $2,100, which also includes comfort headrests and memory settings for the passenger seat.
Minor annoyances are the cheesecloth-like shade for the panoramic sunroof, which admits too much sunlight, and an impossible center-rear seat. There's also some minor harshness felt from the drive train. However, the new air conditioning vents are superb, with infinite adjustments.
Model: 2013 Mercedes-Benz GLK 250 four-door sport utility vehicle.
Engine: 2.1-liter four-cylinder diesel, twin turbochargers, 200 horsepower, 369 pounds-feet of torque.
Transmission: Seven-speed automatic with manual shift mode and all-wheel drive.
Overall length: 14 feet 10 inches.
EPA passenger/cargo volume: 103/23 cubic feet.
Weight: 4,321 pounds.
Towing capability: 3,500 pounds.
EPA city/highway/combined fuel consumption: 24/33/28 mpg.
Base price, including destination charge: $39,495.
Price as tested: $50,735.