Differences between Diesel and Gasoline engines

Being a car enthusiast I’ve always wanted to know more about how a car works. Although my market has plenty of engines using each one of these fuels, I notice that many people still have some misconceptions about them. In this article, we will be going over the differences between Diesel and Gasoline engines.

Introduction: Diesel engines vs Gas engines

In many markets, some wrong ideas might endure even if both kinds of engine are usual.

The doubts and misunderstandings are even greater if your market has few of one of those types of engines.

I will be starting out to referring to two regions where these diesel engines vs gas engines are completely different.

Two different scenarios: Europe vs USA

The USA is known as a country that loves gasoline and where the American V8 is an institution. Diesel engines are not very common among light passenger cars.

Across the Atlantic ocean, things are quite different in Europe.

During the 70’s and 80’s, diesel cars were perceived as slow and noisy. Their black fumes felt heavy polluted and it wasn’t rare to find the rear end of these cars with a film of black soot.

Diesel engines were also bigger and heavier than the gasoline with similar displacement, which meant that a petrol car would need to have chassis reinforcements to be able to cope and handle well with the added weight.

And because the vehicle is heavier, it also needs bigger and more capable brakes.

Diesels require higher production costs in many areas against gasoline cars.

If that wasn’t enough, diesels usually had higher displacements. All of these together made them more expensive.

After reading all of that, you might be wondering what could possibly make you want one? And if in the USA almost every car has a gasoline engine, why is it that less than a decade ago, more than half of the cars sold in Europe were powered by a diesel engine?

Let’s find out!

Is diesel better than gasoline?

While discussing what is the difference between gas and diesel you might be wondering which of them is better. I know, it’s only normal we want an answer to that.

Is diesel better than gasoline? Well, my best answer is that they’re surely different and each one might be more adequate than the other in certain aspects. Let’s see how.

To make it a little more complex, different countries have different conditions. Sometimes the technical matters aren’t the decisive ones on choosing an engine.

The way cars and fuel are taxed by each country are enough to produce big disparities in general consumer behavior.

Maybe barely anyone wanted a diesel a few decades ago as you might’ve realized by now. But still, there were reasons to choose a diesel.

Gasoline engines couldn’t match their efficiency. They couldn’t even come close. This might not seem like much if you have low annual mileage but if your car is used intensively, diesel might pay off.

And diesel engines were more robust, their internals were expected to last longer and tougher usage.

Moreover, they provide more torque which comes very handy when carrying heavy loads.

Gas engines vs Diesel engines

Diesel engines have come a long way since the 70s. Even a 15-year old diesel now today feels a bit outdated. Perfectly usable but not as efficient as current engines.

After these introductory paragraphs, let’s go a bit deeper into various questions that define the good and the bad on the gas engines vs diesel engines matter.

So, what is the difference between gas and diesel? Let’s find out!

A short look at the evolution of diesel

When diesel became heavily used in Europe I started paying more and more attention to them.

Adding a turbocharger to the direct injection diesel engines made their performance rise considerably. Although most times gasoline engines would still be faster in drag races and top speed, diesel’s started showing impressive more muscle for everyday driving situations.

Their superior torque made it feel like there was more engine response available and along with taller gears you would need to change gear less often.

With all the improvements that a modern diesel has, it probably comes as no surprise that most modern of them get back up to speed without a struggle.

Common-rail came along in the 90s and made diesel’s injections become more precise, more efficient and fumes and pollution were also reduced considerably.

A few years later in Europe diesel’s performance was growing enough that it allowed that 1.4 to 1.6-liter diesel units slowly started to become very common. That was especially clear in french carmakers, Renault with their 1.5 dCi unit and PSA (Peugeot and Citroen) with their 1.4 HDi.

As an example, in a matter of a few years, PSA had both a 2.0 HDi with 90 horsepower and later added a 1.6 HDi with 110 horsepower.

More recently, using twin-turbocharging, both Honda and Renault had 1.6-liter diesels with about 160 horsepower.

No, there’s no mistake. I really meant 160 horsepower extracted from small 1.6-liter diesel engines.

Horsepower vs Torque

As I mentioned, the performance of diesel engines was far behind a few decades ago. But in the last 20-30 years that changed dramatically.

Diesels typically still have less power than gasoline engines if we consider similar displacement and forced induction. But diesels were always better at returning more torque.

I heard a quote over 15 years ago which I’ve never forgotten: “People buy horsepower but drive torque”.

Horsepower has a direct relation to your car’s top speed. Sports cars usually have engines that bring out a lot more horsepower than torque. It’s great to feel the engine revving high and performing stronger.

Commercial vehicles and trucks generally are the other way around. Horsepower and top speed are pretty much irrelevant and you definitely are not looking for revving the engine to the redline. What is needed is to move heavy loads efficiently and with the available response, that’s where the torque plays a central role.

Many people take horsepower as if it was the best indicator of a car performance but in most everyday situations you’ll probably spend a very short amount of time using the 2nd half of the rev counter.

Diesel vs Gas engine life expectancy

I remember hearing that diesel engines lasted for longer than gas engines.

According to Universal Technical Institute, Inc., gasoline engines are supposed to start to show internal wear when they hit 120.000-150.000 mile mark. Diesel tends to resist to wear a lot longer, sometimes going over a million miles.

Despite having more torque, diesel engines turn slower. Some gasoline cars can go up to 9.000 rpm (revolutions per minute). Most diesel engines in passenger cars won’t go over 4.500 rpm.

In heavier vehicles like buses, the diesel engines will turn even slower.

That means that for the same given traveling speed, the diesel engine will be turning slower, causing less wear. Efficiency will also be superior, as it’s usual with these engines.

Diesel engines use compression ignition, which means they have to be more robust than a gas engine. That makes them last longer.


Now we’re going over reliability. Let me just start by making it clear that none of these types of engines is necessarily unreliable.

Diesel was generally more reliable because it had fewer parts. For example, diesel engines don’t use spark plugs and related components.

But in recent years they’ve become a lot more complex in order to meet stricter emissions. The famous Volkswagen dieselgate also didn’t help, with some entities wanting to see an end to the diesel engine in passenger cars.

Still, if they’re used frequently in long journeys they should be quite reliable.


Pollution is a matter that has been hand in hand with diesels for decades. Although there’s no way around the facts of the past don’t assume that it’s also true in the modern-day.

During the last decades, diesel technology has improved considerably and they currently feel cleaner than ever.

Still, although the black clouds are becoming rarer, these engines have been having a hard time, partly thanks to Dieselgate. In my humble opinion, that hard time is a bit unfair due to our clean they’ve become in the last few years.

One of the strong points of diesel is in terms of CO2, it’s emissions will be lower than those of a gasoline engine for similar circumstances.


If you were familiar with diesels in the 90s, they wouldn’t pass unnoticed. If you weren’t looking you could even assume the sound was coming from a truck.

Yes, it was quite obvious how to tell the difference between gasoline and diesel cars.

It isn’t that easy to bet on it anymore these days. Modern diesel technology made them a lot more smooth. Vibrations have been strongly reduced and their noise is now considerably hushed down.

Yes, some diesels are still a bit more noticeable but there are others which really will leave you wondering. I’ll go even further and tell you that recently I spent a few minutes on a passenger seat dwelling on what was going on under the hood. Although the drive took about 10 minutes, I had to ask to be sure: it was an oil-burner, not a gasoline engine.


If you had the opportunity to drive a naturally aspirated diesel engine you’d know that performance is not their strong suit. In fact, their performance was one of their weak points and so for years diesels generally weren’t made with small displacements.

If you drive a modern diesel it’s a completely different story.

Turbocharging is one of the reasons for that performance and allows for a great relation between performance and efficiency.

Combining turbocharging with diesel engines improved the usability of these engines considerably.

Fuel prices

In many countries, diesel fuel is more expensive than gasoline. But that’s not the end of the story.

Gasoline engines clearly have some advantages over the oil-burners. But going over the differences between gas and diesel engines we couldn’t leave out the price issue.

Diesel is usually chosen for high usage and might breakeven or even turn more economical in the long run. It will depend on many factors, like the different engines available in each car model, your driving style, and the conditions you drive in, among many others.

Diesel contains more potential energy than gasoline. What that means is that for the same liters of diesel and gasoline, you’ll get more energy with the diesel.

That’s why diesel is more efficient, getting fewer l/100 kms or more mpg and Kms/Litre.

For instance, in the UK, diesel is more expensive than gasoline. Still, a lot of company cars use a diesel engine. All in all, high mileage cars will eventually become less expensive to own and run due to the diesel’s superior efficiency.

Here in Portugal for many years, diesel dominated the market as a liter of diesel is actually cheaper than a liter of gasoline.

Fuel consumption

This article wouldn’t be complete without mentioning the fuel consumption although by now it has become clear to you.

Diesel will be more efficient than gasoline in virtually any situation, for similar circumstances.

For more information, check out my great article on how to calculate your fuel efficiency.

Does diesel pay off?

To be very honest, it really depends. From country to country the prices of cars will be different and so will the fuel prices. You might have plenty of diesels to choose from in your market, or maybe you don’t.

Diesel cars are usually more expensive to buy and some parts might also be more expensive to replace. But for intensive use, their efficiency might justify it.

You can’t guess the costs of your future car but my advice is to always make some calculations in advance comparing both situations to aid you in your choice.

Wrap up

There you have it, I hope you now have a picture of the differences between gas and diesel engines.

Like I said before, despite the differences between Diesel and Gasoline engines, I don’t think there’s a clear winner.

Yes, I do love petrol engines but diesel engines have their advantages, too. They’re just more adequate for intensive and heavy load usage.

Even in medium or larger passenger cars, they make a lot of sense on longer journeys, their performance/efficiency ratio is excellent.