Are diesel-powered cars better than hybrids?

Diesel-powered cars have become increasingly popular in the U.S. over the past few years. But even with its growing status, there are still some misunderstandings surrounding diesel-powered car,  and how they stack up against  today’s alternative drivetrains —  hybrids in particular. Many consumers simply don’t know whether a diesel or a hybrid would be the better way to save money.

Much has been made of Americans’ unwillingness to warm to diesel cars in the past. Images of big trucks with clouds of black smoke billowing from their stacks, or for older Americans, memories of GM’s horrible diesel cars from the 1970s, have failed to inspire much confidence in the fuel. But high fuel prices have Americans looking at more fuel-efficient vehicles, and along with hybrids, diesels are starting to look quite attractive.

Today’s clean diesels are barely recognizable to anyone whose familiarity with the technology stopped the last time automakers tried bringing oil burners to the US market. Gone are the days when diesels belched black smoke, a characteristic  turbocharging technology has helped eliminate.

Sadly, many Americans still envision diesel-powered vehicles as nothing more than loud big rigs and pickups. While in the past, these vehicles were built with the expectation of being loud, diesel passenger cars — which are popular in Europe and on the rise in the U.S. — are not. 

Naturally, there are advantages and disadvantages to both hybrids and diesels, and these factors should be closely considered when choosing which type to buy.

Highway mileage is close enough between popular hybrid models and popular diesels that the way you drive will make more of difference than what you drive. In the city, it’s a different story, as stop-and-go traffic is where hybrids have the advantage. Regardless, where you drive and how much are massively important things to consider.

Where diesels have an advantage is torque. Diesel engines produce huge amounts of torque, hybrids generally do not. So while a Prius and Golf TDI will have about the same amount of horsepower, the Golf TDI produces considerably more torque. This doesn’t  matter much when comparing these particular vehicles, but when the cars start getting bigger and heavier, there is no corresponding decrease in fuel economy with diesels.

For example, the VW Beetle TDI gets 28/41mpg while the bigger Passat TDI, which uses the exact same engine, gets 31/43mpg. The more aerodynamic shape of the Passat gives it an advantage, while its extra weight doesn’t factor into it as much, thanks to the 236lb-ft of torque the engine produces. For a hybrid, moving up to a bigger car would require a bigger engine. For example, the 153lb-ft of torque the Prius produces is barely enough to move the car as it is. This is why German luxury brands so heavily favor diesels for their bigger luxury sedans; the fuel savings are greater than they would be with a comparable hybrid system.

This brings us to the next point, which is batteries. Diesels don’t have them. Not only are they very heavy, but there are other concerns as well. First, they don’t last forever. In fact, their life span is considerably shorter than basically everything else attached to the car. That won’t do you any favors when it comes to resale value, but there are environmental concerns here, too. That’s because batteries use precious earth metals, and the entire recycling process is still terribly inefficient.

This doesn’t outweigh the environmental advantage when compared to most cars that run on gasoline, but this is less true when compared to diesels. The last issue is one of social responsibility. Some of the materials in lithium-ion batteries come from conflict regions like the Democratic Republic of Congo, and even non-conflict mining of materials is often done in appalling conditions. This isn’t true of every battery, but it is something worth looking into if issues of social justice weigh heavily on your purchasing decisions.

Batteries and hybrid systems in general are also extremely complicated and therefore quite expensive. Hybrid models are often noticeably more expensive than vehicles with traditional drivetrains, but what you might not be seeing is that there is often cost-cutting going on in order to bring the price more in line with the competition.

This brings us to the unavoidable fact that diesels tend to be more fun to drive. Try out a Golf TDI and a Honda Insight back to back and you’ll see what I mean.

Of course, the initial cost advantage of diesel is offset somewhat by the higher price of the fuel, so cost just by itself doesn’t give either type of vehicle an advantage. In fact, when comparing popular diesel and hybrids models, the results are startlingly similar.

Edmunds has an excellent true cost to own calculator, and according to this information, a Toyota Prius and Golf TDI will cost almost exactly the same over a five year period once all costs are factored in. Interestingly, they are actually within less than $100 of each other. 

The truth is neither hybrids nor diesels are clearly better than the other across the board. They both have advantages and disadvantages, and your specific needs will dictate which is better for you. If you’re looking for a fuel-efficient, small car to drive mostly or entirely in the city, we’d have a hard time telling you that a diesel would be your best bet.

But there are plenty of people who buy hybrids when a diesel would really suit them better, and for those people, we simply suggest looking at a diesel before making a final decision.

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