In at least the near-term, with the price of Diesel fuel as high as it is, the use of Diesels for consumer vehicles makes little economic sense.
The debate of gas versus diesel raged on for years in the RV and Boating communities. And granted, once you get up to a certain size engine, there is no real choice - you have to go with a diesel. The real "bus" motorhomes and large yachts are all going to be diesels. But these are vehicles costing in the hundreds of thousands of dollars.
What about smaller rigs and boats? What about cars and pickup trucks? In the past, diesel proponents would argue that the increased lifespan and decreased maintenance of a diesel was the big selling point - with increase fuel mileage being the gravy. But these arguments are flawed on two grounds.
First, while it is true that commercial diesel engines can go over 300,000 miles without a rebuild, the reality today is that consumer-grade diesel engines don't last nearly as long. Light truck and car engines are not designed like old-time Mercedes diesels or the Caterpillar tuck engine on an over-the-road truck. The little four-banger in your Golf just isn't the same deal.
And while diesels rarely break, when they do break, they break expensive. It is harder - in America - to find a diesel mechanic who will work on light-duty consumer-grade engines. So you break down in the middle of nowhere, you may be out of luck.
The second problem with the longevity argument is that most people don't keep vehicles that long. Motorhomes don't generally go 300,000 miles - at least not within a few years as over-the-road truckers do. Maybe after a couple of decades, they might approach this, but even then. We've seen a lot of 10 and 20-year-old motorhomes with less than 100,000 miles on the odometer. And the same is true with boats - they end up sitting parked at the dock for long periods of time. Such recreational vehicles don't get exercised like your daily driver.
But of course, gas mileage is the other argument - and one that made sense back in 1980 when cars were getting horrible mileage and diesels were getting great mileage. Diesel fuel was actually cheaper back then as well which was an added bonus. Plus, you were exempt from emissions testing back then, simply because they didn't have the necessary equipment to test diesels. The diesel was an end-run then, but today less so.
Today, diesel fuel is more expensive than gas - by nearly 50%! Gas locally here is $2.14 today, while diesel is over $3. Yes, maybe you might get 50% better gas mileage with a diesel, but you pay 50% more for the fuel - it is a wash. Lately, gasoline engines are being wrung out for every last mpg - with turbocharging becoming very commonplace. As a result, the vaunted fuel mileage gap is closing quickly. A F150 diesel might be rated for 22 city, 30 highway while the gas counterpart is rated for "only" 17 city and 22 highway. In city traffic, the gas model costs less per mile in fuel, and on the highway, the cost is about even (with the gas model still being slightly cheaper) due to the high cost of diesel fuel versus gasoline.
Then there is the purchase cost. Diesels can cost up to ten grand more than their gasoline counterparts. Even "consumer grade" diesels, like Ford's 3.0 powerstroke cost four grand more than a gas model. I would say that four grand buys a lot of gas, but since gas is cheaper than diesel fuel, it really isn't relevant. You end up spending more for the engine and the fuel. You can only hope to make it back in repair costs, over time, which might take a decade or more of high-mileage driving to show.
If you drive for a living, towing heavy trailers, the answer is diesel. If you are Joe Consumer, pulling a boat or a travel trailer for recreation, the answer is less clear - and gas is probably a less expensive and easier choice to live with. If you are commuting to work in a small car, diesel no longer makes sense and may no longer be available.
Yes, the emissions thing. Diesels pollute like mad. Even if you are not "blowing coal" diesels make a lot of soot. Some vehicles actually filter this and have a vibrator on the filter so you can empty out the dust pan of pure carbon powder. Most diesels today use "exhaust fluid" which used to be a snipe-hunt type of joke turned into reality. To reduce pollution, a fluid which contains uric acid is used to scrub emissions. Yes, you are essentially pissing in your exhaust pipe.
All these complications mean the engines are more complicated, have more electronic controls, and as a result are not the bulletproof machines of yore. My old Mercedes W123 was totally mechanical, down to the fuel injection. Once started, it required no electrical system to run and in fact, there was no real way to shut it off, other than to cut off the air supply, which was achieved by a butterfly valve actuated by a vacuum line. If that line came undone (as it did once) the engine could not be shut off. Such was the nature of diesels back then. Today, less so.
Since the VW emissions scandal, which seems to be encompassing more and more manufacturers (such as BMW) it seems that diesels are falling from favor. VW is promising to go all-electric, or at least mostly electric - and other manufacturers are following suit. Diesels for small cars are simply disappearing from the roadways as, economically, they make less and less sense.
Of course, some people are "diesel faithful" such as my neighbor from Ithaca, New York, who thought having a Diesel Jetta was not only cool, but a political statement - which spells trouble right there. Never mind that diesels pollute more than gas engines - he was convinced that somehow his "eco-diesel" was saving the environment. Hey, you can burn fryer oil! But of course, he didn't, as converting fryer oil to diesel fuel is a messy and time-consuming process and, oh-by-the-way, there aren't enough fryers in the world to power even a tenth of a percent of the world's fleet.
Diesels turned out to be a lot about posturing and less about practicality. The leftist drives his diesel VW convinced he is saving the world. The motorhome owner buys a diesel so he can play pretend bus-driver. The pickup truck buyer wants to pay pretend trucker - and scratch his balls while he makes lots of smoke and noise. Outta da way! Diesel trucker coming through!
But the rest of us simply find diesel pickups - particularly ones modified with ridiculous garbage-can sized exhaust pipes that are even louder than normal - to be just annoying and slow.
If you like to read old-time car literature (and who doesn't?) it is interesting to see how many over-the-road trucks back in the day had tiny engines - often gas engines. They didn't go very fast, of course, but they did get the job done.
Many of the diesel drivers of today are driving diesel simply for status reasons. That, and they have issues about their masculinity and need to overcompensate - itself a form of status-seeking. It is also a form of the "professional grade" trap - where people buy overpriced "professional grade" appliances and items, thinking that their experience will be improved, when in fact, it is just made more expensive.
Will diesels go away? Not in the short-term or even the long-term. Odds are, they will continue to dominate heavy-duty trucks and even heavier-duty light trucks. But for passenger cars and light trucks, they will shrink in market share if not disappear entirely, in the case of cars. Certifying diesel emissions will get harder and harder to do, and manufacturers may drop them from even light trucks, if demand doesn't warrant the cost of certification.
I suppose if a manufacturer came up with a high-mileage diesel with low emissions (without cheating) AND the price of diesel fuel dropped precipitously, things might change. And the latter could change, as in America, the high cost of diesel fuel has more to do with refinery design and capacity than anything else. The flood of fracking oil hitting the market is a light, sweet crude, well-suited to making gasoline. But our refineries are set up to crack diesel from heavier, high-sulfur crudes, such as from the middle-east or Venezuela. Changes in politics could change the price of diesel - one way or the other. I am not sure change in technology will occur to overcome the technical problems.
For myself, buying a diesel was not even an option. I simply don't drive enough to warrant the extra cost (and even if I drove a lot, the fuel costs would wash) or haul heavy enough loads to warrant the horsepower. Maybe, someday, if we bought a boat, it might have a diesel engine. But the more I look at the cost of owing boats, the more I think renting them is a nice option.
