How Much Do You Know About Diesel Engines?


By: Robin Tyler

7 Min Quiz

Image: Eugenio Marongiu/Cultura/Getty Images

About This Quiz

Soon after the internal combustion was invented, engineers started looking into alternative fuel sources. In fact, many of the early motor vehicles could run on a number of different fuels, not just petroleum. These fuels included ethanol and kerosene, for example.

But some engineers wanted to devise an engine that would not only run on a different propulsion fluid but also run more efficiently. And maybe it was his German heritage, but one man in particular was driven to strive for this more efficient engine. To do this, he made some changes to the engines of the day. He then tried many different possible propellants. And eventually, although his engine was large, cumbersome and not that powerful to begin, his persistence led to more efficient diesel engines.

And diesel engines are now found in car models all over the world. They have come a long way since those early beginnings as well. In fact, many diesel engines today give performance numbers that are just as impressive as their gasoline-driven counterparts. And then there is the torque! Diesel engines produce a lot of torque. That's why they don't only find themselves powering cars but ships, tanks and locomotives as well.

But just how much do you know about these impressive feats of engineering? Let's see, shall we!

True or false? Diesel engines are more fuel efficient than gasoline engines.

Diesel engines are actually much more efficient than gasoline engines. In fact, gasoline engines are around 20% efficient which means only a fifth of the gasoline in the car drives it. The rest is lost to friction, heat and through other factors. Diesel engines on the other hand, are 40% efficient and sometimes higher.


Who is responsible for inventing the diesel engine?

Rudolf Diesel is credited with inventing the diesel engine in 1894. His early attempts were large, cumbersome and not very powerful. But as time progressed, he managed to make them smaller and more powerful. Today, diesel engine are found in cars, boats and other heavy machinery.


What did Rudolf Diesel first call his new engine?

Rudolf Diesel spent much of the 1890s tinkering with his engine and taking out numerous patents for it. Instead of calling it a diesel engine as we know it today, he called it a "combustion power engine".


At what speed does a diesel engine produce its peak power?

Unlike gasoline engines that produce their greatest power at high revs, a diesel engine is somewhat different. It will produce its best powerband at around 65 mph and at lower revs. This means driving at the highest gear possible so as not to over-rev the engine.


True or false? An early diesel engine created by Rudolf Diesel ran on peanut oil.

Yes, indeed. The diesel engines designed by Rudolf Diesel did, in fact, run on peanut oil. Other diesel engine companies followed the same path, In fact, in 1900, the Otto company exhibited their smaller, more powerful diesel engine which also ran on peanut oil without any need to modify it.


On average, how many miles per gallon will a modern diesel engine produce while you travel?

Diesel engines are infinitely more economical than their gasoline counterparts. On average, diesel engines are producing figures of around 45 miles per gallon for highway driving. This is far better than many gasoline engines, even smaller engines running city cars.


Although diesel has many advantages, it seems not to have caught on in the United States. For every 100 vehicles sold in America, how many diesels equivalents leave showroom floors?

Unbelievable, for every 100 gasoline driven vehicles sold in the United States, only 1 diesel-driven equivalent is sold. When looking at truck figures, the number increases to 10 diesel per every 100 gasoline-powered trucks sold. It's mind boggling seeing that diesel-powered vehicles are so much more economical.


Yes or no? Diesel engines do not need a spark plug to combust the air/fuel mixture in the cylinder.

There are no spark plugs in diesel engines. So how does the air/fuel mixture combust? Well, it is done through extreme compression of the air/fuel mixture. This in turn generates enough heat to cause combustion, resulting in the power stroke of the piston.


What part of the diesel engine is found in no other engine type?

Glow plugs are only found in diesel engines. They form part of the starting process and heat up to ensure first time ignition. This ensures a diesel engine starts first time, even in cold weather.


A 42-gallon barrel of crude oil produces how many gallons of diesel?

From each 42-gallon barrel of crude oil, around 11 gallons of diesel are produced. This is far less than the 20 gallons of gasoline that will come from the same barrel but there is a good reason for that. And that is that diesel is far heavier than gasoline.


What is the compression ratio for air entering a diesel engine?

Of course, compression plays a massive part in a diesel engine. The air must be compressed enough to generate the heat that can cause combustion to take place when fuel is added to the mix. This compression ratio is on to 20 parts per volume.


In a turbocharged diesel engine, what drives the turbocharger?

Once the combustion process has taken place within the cylinder, the gases that are the result of that explosion are released through the exhaust manifold, travel down the exhaust system and leave the car through the tailpipe. When a turbocharger is present, however, some of these gases will be diverted to help power it.


During the four-stroke cycle of a diesel engine, the inlet and outlet valve will be _______ on the combustion stroke.

During the combustion stroke, both the inlet and outlet valve will be closed. Why? Well, it stands to reason actually. The combustion stroke needs the air/fuel mixture to be compressed before the bang! This cannot happen if one of these valves is open because no compression can take place.


For a diesel engine to run perfectly, what are two essential requirements?

A diesel engine is no different from its gasoline-driven counterpart in the fact that the two essential requirements to make it run effectively are air and fuel. If one of these is missing, the engine will never run. Even if the ratio of air to fuel or vice versa is wrong, an engine will not run properly.


What does a thermostat control in a diesel engine?

As a diesel engine heats up while running, it will need to be cooled. Coolant from the radiator is sent through the engine to do just that, retaining the heat from the engine and returning with it to the radiator where it is dissipated. The thermostat controls when this coolant is sent around the engine.


True or false? Diesel fuel was originally a by-product of the making of gasoline.

Diesel is a by-product of making petroleum, but essentially both are derived from crude oil. This is broken down by exposing it to extreme heat which sees it split into various products including liquid and gas forms. Some of these liquids are the start of making diesel and further processes are used to produce it.


In a diesel engine, what does the alternator do?

As in a normal gasoline-powered engine, the alternator's primary purpose is to charge the battery. It also will run the electrical systems on the vehicle including lights, climate control and entertainment system, for example.


Why are the batteries for diesel-engined cars bigger than their gasoline-driven counterparts?

One major area in which diesel engines differ from gasoline engines is that they have a much higher compression ratio. This means they turn over with far more difficulty than a regular gasoline engine on starting. For that reason, they need a bigger battery to turn a bigger starter motor to be able to beat that compression to swing the motor over.


It is possible to jump start a diesel engine. How should the batteries be connected, however?

Like gasoline-powered vehicles, your diesel car can be jump-started by another vehicle if the battery is flat. And you would connect the battery in the same way as you do on a gasoline-powered car, positive terminal to positive terminal and negative terminal to negative terminal.


How would you know that diesel powered car's air filter needs replacing?

The air filter in any car has one task. That is to clear any impurities in the air before it enters the engine. If the air filter needs replacing in a diesel engine, your car could start emitting black smoke from the tailpipe as they are burned during the combustion process. Better get it sorted before it damages the engine.


Coolant in a diesel engine should be changed how often?

The coolant in an engine is necessary to ensure it does not overheat. This liquid should be changed once every year at the very least. Coolant also fights rust and other forms of corrosion within the engine, and in cold climates, stops frost damage.


When performing an oil and oil filter change, why is it necessary to run the engine for a few minutes afterward?

When changing the oil on your vehicle, you will also be changing the oil filter. You will also drain the oil by removing the oil pan plug. It is wise to run a car after the oil has been changed not only to circulate the new oil through the engine but also to check if any leaks have develop.


Diesel engines are not only for cars. Where will you find the biggest diesel engines?

Ships also make use of diesel power. In fact the biggest diesel engine ever made is found on a the Emma Mærsk, a container ship. This engine, the Wärtsilä-Sulzer RTA96-C produces an unbelievable 109,000 horsepower!


True or false? Diesel is highly flammable.

No, this is one advantage that diesel has over gasoline. Other than the fact that it is more efficient than petroleum, it is not nearly as flammable. This fact actually helps make the diesel engine more efficient than gasoline engines. Diesel will burn, as it does in an engine, but its flash point of 205 F means an open flame is not hot enough to do so.


Which of these is a famous name in diesel engines?

Cummings is a massive company based in Columbus, Indiana. Known as Cummings Engine Company, the brand was established in 1919 and is known for its formidable diesel engines including the Cummings B-series, which is widely regarded as one of the best diesel engines ever manufactured.


Older diesel engines can prove to be difficult to start in cold weather. Why is this?

Diesel engines combust the air/fuel mixture through compression. This creates heated air which combusts as soon as diesel is added to the equation. In cold weather, however, the heat generated by compression is far less, thanks to the fact that the engine block is cold which dissipates it.


Which of these below is the fastest diesel-powered car?

The Audi R8 6.0 Quattro V12 is an incredible vehicle. Its 6.0-liter V12 engine pushes out around 500 bhp! That means this mean machine goes from 0-60 mph in just a little over 4 seconds. And it can reach 186 mph. Who needs a gasoline-powered supercar?


In years gone by, diesel emissions were extremely "dirty". What has helped modern diesel engines become far cleaner?

As emission laws became stricter right around the world, vehicle manufacturers had to find ways to ensure that the emissions of their vehicles were reduced. This was achieved by adding catalytic converters to the exhaust system. These converters help draw the harmful emissions from the exhaust gases, which means cleaner emissions leave the vehicle through the tailpipe.


Biodiesel is a form of propellant made from _______?

A replacement for diesel manufactured from crude oil, biodiesel is made out of vegetable oils and fat. These are turned into biodiesel when glycerin is removed through a process known as transesterification. This leaves a product called methyl esters behind, which is basically biofuel.


Which German auto manufacturer was caught up in a diesel emissions scandal in Europe?

In 2015, Volkswagen's diesel engines, particularly the popular 2.0 TDi, were brought into the spotlight when the U.S. EPA accused the automaker of violating the Clean Air Act. This found that Volkswagen diesel engines emitted 40 times more nitrogen oxides in real world driving than when tested in a laboratory.


A diesel-powered engine spewing white smoke out the tailpipe indicates?

A diesel-powered car spewing white colored smoke from its tailpipe indicates that in all likelihood, there is water in the fuel. How can you know for sure? Well, the car's performance can be severely affected. In fact, if you notice the engine beginning to splutter while you try to accelerate and there is white smoke from the tailpipe, then you have watery fuel.


Found only on diesel-powered cars, what removes the soot and from the exhaust gases before they exit the vehicle through the filter?

Diesel engines do produce plenty of waste. A few decades ago, you would sees diesel engines blowing black smoke all of the time. Luckily, modern diesel engines are not nearly as dirty. But they still needed a diesel particulate filter to remove the soot produced by combustion.


A overheating engine that shows no sign of coolant loss indicates what?

A faulty thermostat could certainly be the problem in a engine that is overheating but is not losing coolant. The thermostat will control when coolant is released from the radiator into the engine and if it is not working properly, it will not do this at the correct time, leading the engine to overheat.


In a diesel engine, what causes the air/fuel mixture to combust?

Unlike a gasoline engine where a spark that originates in the coil, travels down the high tension leads and eventually exits through the spark plug and ignites the air/fuel mixture, in a diesel engine, the compression of the air causes it to be heated. At the right temperature, diesel is added into the mix and then ignition occurs.


True or false? A change in altitude does not affect the power output of a diesel engine like it does that of a gasoline engine.

At altitude, because the air is thinner, gasoline engines lose power. This is as a result of less air entering the engine as part of the fuel/air mixture. That means less gasoline is used and power output is lowered. Diesel engines do not have this problem.


Explore More Quizzes

About Autoversed

Welcome to Autoversed: your online auto destination. If you consider a vehicle more than just means of transportation; if you treat your ride with love and care; if, even after years of driving, the feeling of accelerating hard on the open road still gets you revved up – you’ve come to the right place.

Whether you’re a daily commuter looking for a reliable ride, a car enthusiast thinking about your next hot rod, or a parent who needs to get the kids from A to Z, Autoversed has something for you. We’ve got the lowdown on hot exotic rides, pricy luxury vehicles, eco-friendly green machines, rugged off-roaders, and more. Come take a look!