Diesel engines are the perfect power for London taxis, tuna boats, Southern Pacific locomotives and anything built by Kenworth.

But automobiles? Crushed velvet seats and push-button transmissions were an easier sell.

One major problem was perpetual engine clatter that suggested the crankshaft was developing compound fractures. Diesel owners were easily recognized in the dark because their clothes smelled like Kuwait. Everything on any American highway–including joggers and 2-day-old road kills–moved quicker than a diesel car. Whether by GM in the ’70s or Volkswagen and Peugeot in the ’80s.

And these sooty, shaking, pungent engines burn fuel-oil available only at service stations where attendants carry baseball bats and hold $10 bills up to the light.

All of which seems to have been lost on usually astute, traditionally cautious Mercedes-Benz, which has added a 3.0-liter, six-cylinder diesel sedan to its E-Class lineup for 1995.

Stranger still, Mercedes is now selling the E300 Diesel in California, where airtight regulations virtually outlawed such cars for puffing more particulates and bad gases than bonfires and chain-smokers.

But Mercedes–a major player of diesel power since Daimler & Benz trucks in 1923 and the 260D passenger cars three years later–says its new engine meets all California emissions standards and is proof positive that glow-plug technology has cleaned up its act.

By using four valves per cylinder, by positioning the fuel preparation prechamber above the center of the piston face, combustion is fuller, more evenly distributed and much more efficient. So particulate emissions, i.e. smoke from unburned fuel, are reduced. As is engine clatter, even during cold weather starts.

A system of exhaust gas recirculation plus a ceramic catalytic converter–rare in diesels–further reduce those elements that offend eyes, bronchiole and the state Air Resources Board.

And diesel fuel has changed. Now there’s a lite fuel that’s low on sulfur. There goes most of the whiff of eau d’Arabie.

Double overhead cams and multivalve technology–whether on gasoline-powered or diesel engines–always increase mechanical muscle. With the E300, they produce 134 horsepower, a solid boost on the 121 horses of the five-cylinder, 2.5-liter diesel Mercedes has been selling in the United States–but not recently in California–since 1974. And that little workhorse was turbocharged.

The new engine’s major attraction, however, is fuel economy.

Mercedes’ E320 sedan burns super premium gasoline and delivers 19 m.p.g. in town and 25 m.p.g. on interstates. The E300 is powered by diesel costing about the same but squeezing 26 city and 32 highway miles from each gallon.

With a fuel tank holding 23.8 gallons, that translates to a minimum of 750 miles between fill-ups–or traveling from Los Angeles to Albuquerque without stopping for anythin g but coffee and personal recycling.

Peter Patrone, product manager for the E-Class, thinks that the public misperceives diesel cars and says that the E300 is overdeveloped in terms of durability and reliability:

“Overall, we have sold 500,000 diesel cars in the U.S. market, with the bulk of 370,000 since 1978. About 93% of those diesels are still on the road . . . and our one-million-mile car is a diesel.”

But despite vast improvements, no Mercedes diesel sings as softly as a Lexus 400. Light it up in a garage, and one realizes that even low-sulfur fuel could use a good deodorant. Exhalations of engine and tailpipe still leave a faint layer of fine soot on the trunk, and, oddly, heavier, blacker slicks of carbon on its beautiful cast-alloy front wheels.

Owners will need the E300’s extended range because service stations pumping diesel fuel are entire neighborhoods apart. And 0-60 m.p.h. acceleration time of 13.7 seconds means most subcompacts will have its lunch.

Why buy one?

Durability, reliability and the length of its legs are obvious advantages. At $40,000, the E300 also is $2,500 cheaper than its gasoline-propelled counterpart. Which, it must be noted, is no longer overpriced when compared to the $50,000 sticker shock of a Lexus or Infiniti.

And no matter the plumbing under the hood, the car carries every nuance and all the aura of a Mercedes; from an elegant hush and stolid ride to its broad hint of being handcrafted for each buyer.

But final success rests with the legion of diesel disciples, individualists all. Most are repeat owners with enormous dedication to type. They prefer practicality before prestige. They care not one whit of being several kilometers left of mainstream.

“They are fanatically loyal,” Patrone notes. “And we have no intention of deserting them.”

Apart from a chromium “Diesel” cutout on the rear deck, the mid-size E300 shows neither internal nor external differences from gasoline-powered members of the mid-size E-Clan.

Outside are lines of the simple three-box design that is a Mercedes tradition, but softer and rounder these days. The interior is leather and wood with all control noises muffled, even silenced as the payoff of precision engineering. Which nobody does better than Mercedes.

Driver- and passenger-side air bags are standard. So are anti-lock brakes, automatic air, power windows, alarm, central locking and cruise control. But there’s no remote trunk release and a north-to-south transmission hump will buckle the legs of the center member of any rear-seat trio.

The car certainly is no performance monster, not from rest, not when one is trying to be innovative in the middle ranges. It certainly never sounds quite right. Fuel grime is still visible.

The essential truth is that if a fan of diesel motoring, this is a vehicle to buy as a 10-year purchase. Those with no allegiance to the memory of Rudolf Diesel will not be converted.

Diesel driving is indeed an acquired taste–rather like bratwurst and dark beer.

“But,” Patrone says, “the car doesn’t give you as much gas.”

1995 Mercedes-Benz E300D

The Good A lifetime between fill-ups. Cleaner, quieter, more efficient diesel engine. Pomp, elegance with world-class engineering. No longer overpriced, always fully loaded.

The Bad A mite noisy. A little sooty. A whole lot sluggish.

The Ugly White-gloving the trunk lid after a long run.

Cost Base and as tested: $40,000.

Engine 3.0 liter, 24-valve, in-line six-cylinder diesel developing 134 horsepower.

Type Front-engine, rear-drive, mid-size luxury sedan.

Performance 0-60 m.p.h., as tested, 13.7 seconds. Top speed, estimated, 120 m.p.h. Fuel consumption, EPA city and highway, 26 and 32 m.p.g.

Curb Weight 3,525 pounds.