The Diesel Dilemma

By Eric Peters, Automotive Columnist

The last time people began to sweat the cost of gas, they were able to turn to diesels. The cars delivered tremendous mileage (e.g., a VW Rabbit diesel was capable of 50-plus MPG, as good or better than a new Prius hybrid) and — perhaps as important — the fuel itself was cheaper than gasoline.

You may recall.

What happened?


Diesel fuel became more expensive than gasoline — because of government edicts that made it more rather than less expensive to refine. Today’s “ultra-low sulfur” diesel runs close to $4 a gallon in my neck of the Woods vs. just over $3 for a gallon of regular unleaded.

This cost-to-feed disparity takes a lot away from the economic argument in favor of buying a diesel-powered car. Especially given that modern diesel-powered cars — though excellent in many ways — are also a great deal less fuel-efficient than the diesel powered cars of the ’70s and ’80s (the era before government got around to hassling diesels to the extent that it had been hassling gas-powered cars). Engine design had to be altered; exhaust systems changed up. Almost all current-year diesel-powered passenger cars have particulate traps and “regeneration” (diesel fuel is injected into the exhaust to after-burn it for emissions control reasons; of course, fuel used to burn off soot is fuel not used to propel the car — and your mileage goes down).

Most (virtually all) current-year diesel-powered passenger cars also require something called Diesel Exhaust Fluid (DEF) to achieve compliance with emissions regs. That is, to placate the government (at your expense). The DEF — basically, urea — is contained in a separate tank that must be regularly topped off. The DEF works kind of like a gas engine’s catalytic converter, chemically altering the composition of the exhaust stream.

Whether this is good or bad is ultimately neither here nor there as far as the consumer appeal of diesel-powered cars.

Historically, the primary reason for going with a diesel rather than a gas-engined car (all else being equal) was the prospect that the diesel would — hopefully — save you money.

Unfortunately, that’s less likely today than it was yesterday. Because of the higher cost of the fuel — and the lower fuel-efficiency of modern diesels.

Here’s an example:

I recently reviewed the 2014 VW Jetta TDI (see here). For a modern car — relative to other modern cars — it delivers excellent fuel economy: 30 MPG in city driving and 42 MPG on the highway. But back in 1979, a VW Rabbit diesel delivered 45 MPG … in city driving.

And 57 on the highway.

See here, if you don’t believe me.

Now, granted, the ’79 Rabbit is (was) a smaller car than the ’14 Jetta. But the difference is startling nonetheless — because the Jetta has all the putative advantages of the intervening 40 years (almost) of technological advances.

Shouldn’t it deliver better economy than a Carter-era car?

Well, it could.

If VW were not forced to festoon its brilliant TDI (turbo direct injection) diesel with all the foregoing folderol. If the federal obsession with soot — aka “particulate” emissions — were not so fervid. And here it is important to point out that diesel emissions are different. Particulates may be obnoxious to some, but they are not a factor in the formation of smog — the main justification for swaddling gas engines with a Hannibal Lecter-esque suit of “controls” to tamp them down.

Everything — like it or not — is ultimately a cost-benefit analysis. And frequently there is a conflict between one desired thing and another desired thing. In this case, the desire of the government to effectively curb tailpipe emissions of cars (both diesel and gas) to nil conflicts with the consumer’s desire for a fuel-efficient (to say nothing of affordable) vehicle.

And this is why — for the most part (the Jetta I reviewed being one of literally two exceptions) the diesel-powered cars available today are almost all high-end/expensive cars. The diesel engines available in vehicles like the Mercedes E-Class and the BMW 3 and 5 are touted as much for their performance as their economy — and of course, the cars they’re installed in are sold on the basis of luxury and status. These are the sweeteners that make so-so-efficient modern diesels more palatable to buyers.

But on the economy end of the scale, it is harder to make a sound case for a modern diesel-powered car. Even the thoroughly excellent Jetta TDI. It costs about $5k more than the base trim gas-engined Jetta. And then there’s the 50-75 cents more per gallon you pay at the pump. Sure, the TDI’s mileage is 10-plus MPG better than the gas-engined model’s. But $5k buys oceans of gas … and don’t forget the extra $8-10 or so more you’ll be paying at each fill-up, diesel vs. regular unleaded.

To sum up:

The proverbial low-hanging fruit was plucked decades ago. That is, on the order of 90 percent of the harmful (e.g., smog forming, respiratory distress-inducing) byproducts of internal combustion were “controlled” by the first simple — but very effective — emissions technologies, such as catalytic converters (for gas-engined vehicles). Since the ’90s, the government’s increasingly demented crusade has been to “control” the remaining fractional part of a vehicle’s exhaust output that is less-than-pure.

I italicize this for emphasis because it is not a literary or editorial flourish. It is the literal truth. The government will push for — and impose — a new round of emissions rigmarole in order to “cut” what they will invariably describe as “harmful emissions” by half a percent. But they will tout this as a 50 percent reduction — which it technically is. Because if you reduce 1 percent by half you have reduced it by 50 percent. But “50 percent” sounds a helluva lot better, PR-wise, than “half of one percent.”

So, we end with pretty pricey diesels that are only so-so efficient — relative to what they should and easily could be.

And we get to feed them fuel that is likewise more expensive than it should and could be.

This from a government that constantly crows about the importance of being conscious about the energy we use — and which tub-thumps metronomically for “more efficient” vehicles.

If any of them knew how to read a dipstick, things might be different.


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Leave a Comment

9 Responses to “The Diesel Dilemma”

  1. Jason Larke says:

    You need to remember that ratings aren't comparable across years due to EPA cycle changes. Their compare tool doesn't go back to 1979, but their calculated corrected figures for the 1984 Rabbit diesel bring it from 42 city / 48 highway / 45 combined to 35 city / 43 highway / 38 combined. The current Jetta diesel automatic gets 30/42/34.

    I wonder how much of the relative loss in fuel efficiency between older and more modern cars comes from emissions controls vs crash safety features vs essentials required for the modern marketplace. I suspect that a car on sale in 2014 with 1984 levels of performance and NVH would sell quite poorly regardless of other considerations.

    • seenmuch says:

      Being someone who owned and drove many Rabbit Diesels 10s of 100s of thousands of miles over the years I can say the original unadjusted epa numbers on this car's rating were closer, a lot closer to reality.

      It was really hard if not impossible to make one of these get below 40-43 mpgs with little regard to where and how fast or slow you drove. And if you kept speeds lower you could without effort top the 50 mpgUS mark tank after tank…..

  2. Lava says:

    A cost-benefit analysis is usually the cost and benefit to consumers. The government-consumer conflict is called something else.

    The cost-benefit ratio to the consumer is the consumer's desire for cleaner emissions versus the desire for cheaper cars. Consumers desire less smog too.

  3. seenmuch says:

    Your article is spot on a few points but not on others. The issue is the current epa rating is low by as much as 30 % depending on driving conditions and the transmission.

    The manual trans always see at a minimum 15-20 % above the current similar with the DSG automatic sequential shifting dual wet clutch manual transmissions.

    Real World numbers are:

    DSG non-urea equipped cars, 34-36 city/ 38-42 mixed/ 42-50 highway

    6 spd Man non-urea equipped,38-42 city/ 40-46 mixed/45-52 highway

    In the much larger heavier-Passat urea equipped

    12-14 DSG: 35-41 city/ 38-44 mixed/ 42-49 highway

    12-14Man: 38-43 city/ 40-45 mixed/ 44-52 highway

    The 2015 Golf VII is now getting a urea using more powerful less fuel sipping engine, it is on average 25-30 % more fuel efficient than the current non-urea equipped engine. Not relying on the still less than useless current epa rating that does by the way show a increase this engine is currently seeing real world 10-15 % above the 2014 Passat TDI real world numbers…

    The entire line of current 130hp/236lb-ft diesel engines are going to be getting this 150hp/236lb-ft engine by the end of the 2015 model year.

    Right now this engine is in the 2015 Passat and Golf VII TDIs is seeing a significant increase in mpgs over the older design engine cars. These cars that have this new engine are on sale right now.


    Also the 2014 Jetta TDI is from a design a few years ago, 2008( the 2009 model year)………. This was a time when automakers thought it was better to go with a engine design that used more fuel meet current ridiculous emissions standards. They thought that the public would not accept an emissions system that required their input in the urea tank refilling.

    But today conditions have changed and they now know that the public is up to dealing with keeping the urea tank full. In this design less fuel is required to meet emissions.

    A perfect example of this is in the 12-14 Passat TDI, the most fuel efficient car in the current VWAG diesel lineup. With all of the cars in the VWAG diesel powered lineup getting a urea designed emissions again the smallest car in the lineup, the A7 2015 new Golf will be the most fuel efficient. The VW Jetta, the New Beetle, Golf, & Passat and the will also see a significant increase.

    • seenmuch says:

      the Audi A3 Sedan TDI is also getting this higher output urea equipped engine that achieves higher mpgs over the previous model that had the 2008 design engine that used extra fuel to make the emission equipment function within current limits.

  4. tz says:

    "the era before government got around to hassling diesels to the extent that it had been hassling gas-powered cars"

    I will take issue with your snark. I remember pre-emission control days. This so called "hassle" is entirely necessary and desirable.

    I can remember when I would get in out of rush hour traffic and my clothes reeked of unburnt hydrocarbons. I remember Denver having a small fraction of the traffic it does today, and with equal or worse air pollution.

    • seenmuch says:

      The government blindly blamed diesels for the brown cloud in Denver you speak of when they were never to blame.

      The EPA did a study to find the cause of the brown cloud a few years back. It turns out that diesels had very to do with the production of the brown cloud, but had been unfairly targeted as the cause without science to back up that claim. The larger diesel engine produced pms did not stay in the air long enough to cause issue. The diesel engine produced PMs were larger and heavier so fell harmlessly to ground in hours of being expelled.

      The study discovered that the main causes for the pollution that lead to the brown cloud were power plant and gasoline engine produced ultra-fine PMs. These ultra-fine PMs stayed in that air for days and weeks leading directly to the brown cloud. Also the sand and grit that was mixed in with salt to help increase traction on frozen roads also ended up in the air making the brown cloud worse. They stopped using solid deicers a few years ago. The state stopping use of these deicers has been shown to have had the biggest impact on improving winter air quality in the Denver metro area.

      AS we have increased regs on diesels it has come to light that gasoline engine produced, unregulated today ultra-fine PMs are the main cause today in production of arosolized particulates. Diesels make up less than 1 % of what is on the road today in light duty autos so have never been the pollution issue many assume they are. If we are serious about making the air cleaner, which this current effort to overstrict diesel emission has not the regulations must be put into place requiring PM traps be installed on all gasoline burning engines. With gasoline power making up 99 % of what is on US roads only by cleaning up the exhaust of these vehicles can we expect to make the air cleaner.

  5. Glenn says:

    Eric Peters is correct! I had a 1980 (or s)o diesel Rabbit that got 50 mpg on the highway! Diesel cost half as much as gas then!

  6. Peter says:

    Diesel is not more expensive to refine than gasoline, and this, if it were true, would not be the reason it is more expensive than gasoline today. In reality, both are more expensive to refine for the same reasons: regulations. But diesel has become more expensive simply because in requiring it to be ULSD or ultra low sulfur diesel, it is marketable internationally as a refined product. The price on the open international market is higher than the gasoline we make/import. There is a glut of gasoline in the refining world simply because diesel is more desirable internationally. Gasoline originally was and still is a byproduct of refining kerosene (close to diesel BTW) and now Europe sells us their surplus gasoline while we export refined ULSD. Its really that simple.