In September 2015, news broke that Volkswagen had been covering up illegally high emissions of nitrogen oxides from its diesel vehicles.
That changed the world of diesel forever.
Since then, various groups have called for diesel to be heavily taxed or even banned altogether.
Many commentators say that diesel was mis-sold to buyers, who were promised low emissions and high fuel economy, when, in reality, it was totally unsuitable for the journeys they do.
But diesel isn’t necessarily the bad guy. For some buyers, it still makes an awful lot of sense. But how do you know if you’re one of those buyers?
What’s your mileage?
Diesel cars make sense for high-mileage drivers. Those doing over 32,000km a year will soon benefit from the increased fuel economy a diesel engine provides — and, over time, they’ll save money.
This is because diesel fuel contains more energy than petrol, meaning that it offers more miles per gallon. However, in most cases, diesel variants of cars cost more to buy than their petrol equivalents, so, depending on the price gap, you’ll need to do more miles to break even.
For example, the Volkswagen Golf, 1.6-litre diesel costs more than the equivalently powered petrol. According to the official fuel economy, a driver would break even after 120,000km. For an average driver, that’s over six years. But a motorway mile-muncher doing about 48,000km a year would break even in less than three years.
What type of journeys do you usually do?
Diesels are very efficient, when they’re warm. However, they take a while to heat up, which means during the first 15km or so of any journey, they’ll be inefficient and polluting.
That’s not good if you regularly undertake lots of journeys shorter than that, and it gets worse, too. You see, modern pollution control systems need the engines to be running at a certain rpm to function.
This is easily achievable on the motorway, but if your car starts a regeneration cycle while you’re idling on the school run, you risk clogging up expensive and complex systems, such as exhaust gas recirculation or diesel particular filters.
How heavily loaded are you?
If there’s one thing diesels have over a petrol in abundance, it’s torque. This sheer pulling power means that for heavily loaded vehicles, such as people carriers, vans, or trucks, there isn’t much substitute for a diesel.
That’s especially true of people who often tow heavy items, like caravans or horse boxes. A petrol, unless it’s a super-powerful one, struggles in these situations.
A diesel is more pleasant to use when loaded to capacity, and won’t suffer as much strain as a petrol would. You won’t need to ride the clutch so often, nor will you need to row through the gears at such a rate.
Which cars are you looking at?
Of course, this all assumes you have an option. However, several cars simply don’t offer a viable alternative to diesel, leaving you with the choice of sticking with the oil-burner or choosing a different car.
Move into the more luxurious end of the market and you may find the diesel is the sensible option. Sure, there’s a petrol available, but it’s a monstrous V8 with a daft amount of horsepower, and a fuel economy figure in the teens.
In these situations, you may just have to work around a diesel, taking regular long journeys and making sure it’s impeccably serviced to keep the emission control systems running as they should.
Many drivers of diesel cars today would be better off in a petrol, or even an equivalent hybrid or electric model. Yet, the fuel has its uses, for high-mileage, heavily-laden, or penny-pinching buyers.
As always, just shop carefully and consider all of your options before you buy.