As you may already be aware of, diesel engines are
more efficient than gasoline engines of the same
power, resulting in much lower fuel usage. For an
efficient turbo diesel, the average is 40% more miles
per gallon. The higher compression ratio with
diesel engines help to raise efficiency, but diesel
fuel also contains around 15% more energy per unit
volume than gas.
Diesel engines that are naturally aspirated are far
more massive than gasoline engines of the same power
for two reasons. First, it takes a larger capacity
diesel engine than a gas engine to produce the same
amount of power. Essentially, this is because the
diesel can’t operate as quickly. The rev limit is
slower, because getting the correct fuel to air ratio
into a diesel engine fast enough is more difficult
than a gas engine. The second reason is due to the
fact that a diesel engine needs to be stronger to
withstand the higher combustion pressure needed for
Diesel engines also produce very little carbon
monoxide as they burn the fuel in excess air except
at full loading capacity, where a full quantity of
fuel is injected per cycle. They can however,
produce a black soot from the exhaust, which consists
of unburned carbon compounds.
Often times, this is caused by worn injectors, which
don’t atomize the fuel sufficiently enough, or a
faulty management system that allows more fuel to be
injected that can then be burned with the available
For commercial use that requires towing, diesel
engines tend to have more desirable torque. Diesel
engines tend to have their torque peak quite low
in their speed range which provides smoother control
over heavy loads when starting from rest, crucially
allowing the engine to be given higher loads at low
speeds than a gas engine.
The lack of an electrical ignition system in diesel
engines improves the reliability. The high durability
of diesel engines is also due to the overbuilt
nature as well as the combustion cycle, which will
create a less violent change in pressure when
compared to a gasoline type spark ignition engine.
Diesel fuel is also a better lubricant than gasoline,
so it is less harmful to the oil film on piston
rings and cylinder bores – making it routine for
diesel engines to go 250,000 miles or more without
having to be rebuilt.
For several reasons, diesel proves to be better than
spark engine ignition. Diesel engines last a lot
longer, they offer more torque, and they are also
more reliable. They are also more expensive as well,
although you get what you pay for. If you have
never owned a diesel vehicle, you owe it to yourself
to see everything they offer you – and you’ll find
yourself a very satisfied customer.
A diesel engine will go much farther on a gallon
of fuel that the standard gasoline engine
because of their designs, and due to the higher
energy density of a gallon of diesel fuel. But,
it also takes a bit more oil to manufacture a
gallon of diesel than a gallon of gas, with
the production and refining processes for
diesel producing more gases that trap heat.
Therefore, when you consider the relative merits
of deisel and gas cars, try knocking the MPG
estimates for the diesel car down by 20 percent.
A diesel vehicle will cost you a bit more,
so you’ll get more bang for your buck from a
The nasty rumors you hear about diesel are
true as well – diesel is less refined than gas,
or in other terms it’s dirtier. Diesel
vehicles also emit more particulate matter and
NOx, both of which are serious health hazards
and air pollutants. Current diesel engines are
more polluting per each mile they are driven
than gas engines.
Using biodiesel on the other hand, will improve
this situation. If biodiesel is available in
your area, you’ll still need to examine
whether a diesel is the right vehicle for you.
When you consider the facts, you have to ask
yourself which models you can afford, what is
the MPG, will engine be succifient for you,
and the number of passengers the vehicle will
accommodate. Then, given your budget, you can
go from there.
There are numerous gas and diesel vehicles
available, all you have to do is decide which
one is right for you. If you research carefully,
you’ll have the perfect vehicle for your entire
The designs of diesel engines striving to increase
performance have made a lot of advancements in engine
fuel delivery to the combustion chamber. The diesel
engines of today are much quieter, smoother, and
also more powerful. The quality of diesel fuel on
the other hand has not advanced at the same rate as
the improvements of engines.
As soon as it is produced, diesel fuel begins to
deteriorate. Less than 30 days of refining, all
diesel fuel, regardless of the brand, goes through a
natural process called oxidation. This process forms
varnishes and gums in the fuel by causing the
molecules of the fuel to lengthen and start bonding
Now, these components will drop to the bottom of the
fuel tank and form diesel sludge. The fuel will
begin to turn very dark in color, smell bad, and
cause the engine to smoke. The engine starts to
smoke as some of these clusters are small enough to
pass through the engine filtration and on to the
As the clusters begin to increase in size, only a
small amount of the molecules will get burned, as
the rest will go out the exhaust as unburned fuel
Its estimated that eight out of every ten diesel
engine failures are directly related to poor quality
and contaminated fuel. The build up of contamination
in the fuel systems and storage tanks can clog
filters, thereby causing the engine to shut down,
and damage to the engine to occur.
The number one reason for bad fuel is due to the
increasing popularity of diesel power and the
accompanying increased demand for more diesel fuel.
Long ago, diesel fuel remained in the refinery
storage tanks long enough to naturally seperate and
begin to settle, allowing the clean fuel to be
drawn apart. Now, with the demand getting higher
than ever, the fuel is never stationary long enough
to settle, and the suspended water and solids are
passed on to the person buying the fuel – you.
The changes in refinery techniques is also a
problem. In order to get more products, diesel
fuel is being refined for more marginal portions of
the crude barrel. This results in a lower grade
product that is thicker and also contains a lot
As time continues to pass and technology gets better
and better, one can only hope that the quality of
diesel fuel improves. As it stands now, the quality
isn’t good at all. If you run diesel fuel, all
you can basically hope for is that the fuel you
are getting isn’t contaminated.
Over the years, the prices of both gas and diesel
have experienced some drastic changes. Many years
ago, the price of gas was around a dollar or a
little more, nothing like it is today. Back then,
gas wasn’t high in price although the demand for
vehicles wasn’t what it is today either.
As the demand for vehicles grew, the demand for
fuel grew as well. Other actions and events have
played into the equation as well, resulting in
the rising costs of fuel. Fuel is something we
all need to run our vehicles, as we wouldn’t be
able to go anywhere without it.
As you may know, a majority of the gas we get at
local gas stations comes from overseas, primarily
the Middle East. Therefore, we have to pay taxes
and such on the gas we use, which pays for the
gas as well as the shipping. If we got our gas
from within the United States, one can’t help
but wonder whether or not the prices would indeed
Diesel on the other hand, has always managed
to keep a price lower than gas. Diesel comes
from within the United States, so the prices are
of course going to be lower. The only problem
associated with diesel fuel is locating it, as
many gas stations don’t sell it.
When it comes to the choice between the two,
diesel fuel is obviously cheaper to buy. Gas is
in supply more, which means that you can find
it almost anywhere. If you own a gasoline
vehicle, you obviously don’t want to put diesel
in it. If you own a diesel vehicle, then you
of course wouldn’t want to put gas in it either.
If you’ve owned a diesel powered vehicle in the
past or if you own one now, you no doubt appreciate
the qualities this engine provides you with. More
torque, better fuel economy, and easier maintenance
are but a few of the attributes of owning diesel
However, there are some motorists that still
complain about the engine’s weak power, especially
when accelerating from a full stop. What you
may not be aware of is the fact that a diesel
engine can be tweaked to give more power without
harming the fuel economy.
Diesel engines use air compression to create
combustion versus the fuel/air mixture that is
required by gas engines. This attribute means
that diesel engines don’t require spark plugs
and therefore don’t need to be tuned up.
Diesel fuel has a much high fuel density than
gas, which results in fuel economy increases
of 20 – 30% over gasoline powered vehicles.
Diesel engines are also cheaper to maintain as
they have less parts than that of a gasoline
powered engine. The life span of a diesel
engine is also much longer.
If you’re looking for torque, for pulling a
boat or other equipment, then the diesel
engine has the supreme advantage. Diesel
engines are surely slower, especially when
starting from a dead stop, although when you
climb hills or go over bridges, the diesel
engine is surely up to the task.
With trucks, diesel is normally the leader
over gas engines in terms of performance and
miles per gallon. Diesel trucks will get
more miles than gas trucks, and the price for
diesel is a bit cheaper than gas these days.
And with gas prices on the rise, diesel will
continue to dominate for a long time to come.
With diesel engines, the compression ratio is higher
and there is more power. From a technical point, the
compression ratio of an engine is the comparison of the
total volume of the cylinder at the bottom of the
piston’s stroke divided by the volume of the cylinder
remaining at the top of the stroke.
Serious damage to gas engines can occur if you attempt
to run a high compression ratio with a low octane type
of fuel. Detonation is the ignition of the fuel due
to the high temperature caused by a high compression
ratio that is developed by design. The fuel is
ignited prior to the spark of the plugs that result
in a rapid, yet uncontrolled burning.
Keep in mind, the diesel is a heat engine, using heat
developed from the compression of air. High compression
ratios are possible since the air is compressed. The
hot compressed air is sufficient to ignite the diesel
fuel when it’s finally injected near the top of the
Fuel and air in the design of diesel engines are not
premixed outside of the cylinder. Air is taken into
the cylinder through the intake valve and then
compressed to make heat. The diesel fuel is injected
near the top of the piston’s stroke in an amount or
ratio that corresponds to the load on the engine.
The higher compression ratio causes engineers to
design, and test the block, heads, head bolts,
crackshaft, connecting rods, rod bolts, pistons,
piston pins, etc., with a greater range of structural
capacity. To put it in other terms, diesels are
heavier than gasoline engines.
Deciding on gas and diesel can be tough, although
there are several reasons why you should use diesel.
1. Diesel engines produce twice the power
per gallon of fuel than gasoline.
2. A gallon of diesel is normally cheaper
than a gallon of gas.
3. Diesel fuel doesn’t blow up. The fact
is, its hard to get diesel to burn at all.
4. Diesel engines will last four times
longer than gasoline engines.
5. Diesel fuel that is untreated will last
longer in storage than untreated gasoline.
6. Treated diesel fuel will last longer in
storage than treated gasoline.
7. Diesel fuel treatment will cost less
than gas treatment.
8. Spoiled diesel can be reconditioned to
refinery specifications, as spoiled gas can’t.
9. Unmodified diesel engines can be ran on
There are very few engine configurations that promise
increased fuel economy and power. There are few
engines that offer this in addition to reliability.
Today, those across the ocean are enjoying the
fruits of diesel technology revolution.
Diesels have experienced a great history here in the
United States. In 1980, General Motors modified
their 350ci gas V8 to run on diesel fuel. The result
however, wasn’t that god. These engines offered
better fuel economy but little else. They were
very slow, and not very reliable.
Mercedes Benz on the other hand, had better luck
in the 1980s with an array of vehicles available
with diesel engines. These great vehicles offered
amazing durability although they were rough, noisy,
and smoked quite a bit. Volkswagon offered diesel
as well, although they had a habit for spewing
blue smoke from the tail pipe.
Throughout the 90s, Benz and Volkwagon offered
diesel vehicles in the United States, with each
generation becoming cleaner, smoother, and more
powerful than the last. Overall, they were a
tough sell as they still lacked the horsepower
that many were seeking.
Today, Mercedes, BMW, Jaguar, Volkswagon, Ford,
and many other manufacturers are offering diesels
to many markets throughout the world. To put it
simple, forget everything you know or think you
know about diesel engines in the United States.
These newer engines benefit from hundreds of
technical innovations. There are several diesels
in Europe that offer better acceleration than
their gasoline counter parts. BMW’s 120d has
163bhp, goes 0 – 60 in under 8 seconds, and
achieves 49.6 miles per gallon.
Benz offers the C320 CDI SE that has 224bhp, and
over 360 lb foot of torque. This car gets just
under 48 mpg on the highway, with an acceleration
of 0 – 60 in under 7 seconds. Throughout North
America, you won’t find a gasoline engine that
offers this unique blend of fuel economy and
The reason why diesels haven’t caught on in
North America comes down to one word – sulfur. We
have too much sulfur in the diesel here in the
United States. This cheap grade of diesel fuel
will run havoc on the more sophisticated diesels
offered overseas and cause an increase in
There is hope however, as refiners will soon be
producing what is known as ultra low sulfur
diesel fuel. This will help to reduce the sulfur
content from 500ppm to 15ppm.
When gas is compressed, the temperature of it will rise,
with diesel engines using this very property to ignite
the fuel. Air is then drawn into the cylinder and
compressed by the rising piston at a much high
compression ratio than gas engines, up to 25:1, with
the air temperature reaching 700 – 900 degrees C.
At the top of the piston stroke, the diesel fuel is
injected into the combustion chamber at high pressure,
then through an atomizing nozzle, it mixes with the
hot high pressured air. The resulting mixture will
ignite and burn very rapidly. This combustion will
cause the gas in the chamber to heat up rapidly,
which increases the pressure and forces the piston
The connecting rod will transmit this motion to the
crankshaft. The scavenging of the engine is either
done by ports or valves. To get the most out of
a diesel engine, use of a turbocharger to compress
the intake of air is vital. You can also use an
aftercooler or intercooler to cool the intake air
after compression by the turbocharger to further
increase your efficiency.
An important part of older diesel engines was the
govenor, which limited the speed of the engine by
controlling the rate of fuel that was delivered.
Unlike gas engines, the air that comes in is not
throttled, so the engine would overspeed if this
wasn’t done. Older style injection systems were
driven by a gear system that came from the engine.
The diesel engine is truly an advancement to vehicles
as we know it. As technology gets better, you
can expect the diesel engine to get better as well,
possibly even proving just how much better it is
to the gasoline engine.
Due to the high compression ratios and resulting
high cylinder pressure in diesel engines, they
must be built to withstand a lot more punishment
than gas engines. The parts that are spruced up
include a thicker block and cylinder heads,
pistons, crankshaft, and valves, which can be
very costly indeed.
When it comes to the price, gas wins this one by
far. Diesel costs a lot more to own than gas,
which is one of the main reasons why people tend
to choose gas over diesel.
Diesel fuel is easier to refine, taking less
time to get from raw petroleum to final product
from gas, giving it a lower price than that of
gas. On the other hand, within the United States,
diesel is priced the same or just a bit below
regular unleaded gas.
Noise and vibration
Despite many improvements in noise isolation and
engine noise technology in trucks over the last 10
years, diesels are still much louder and shake
more than gasoline powered vehicles. At idle, the
clatter and shake of diesel vehicles are clearly
noticeable, while it can be hard to tell if the
gas engine is even running.
If you’ve tried to start a diesel engine on a
cold day, you know that gas is by far easier to
start. Diesels don’t have spark plugs like gas engines
do, as the fuel is ignited once it’s injected into
the cylinder that is already under pressure.
When it gets cold, the air isn’t hot enough to
ignite the diesel fuel.
Maintenance on a diesel vehicle is more expensive,
thanks to many things including the larger volume
of oil in the engine and the fact that fuel filters
and water separators must be serviced more often
than gas vehicles. Gasoline engines have a bigger
advantage due to extended service periods on spark
plugs, engine oil, and even antifreeze.
Making that final choice between gas and diesel comes
down to what you’ll do with your vehicle and where
you live. If you use your vehicle for quick, fast
acceleration and rarely ever haul heavy loads, and
don’t plan to keep your vehicle past 100,000 miles,
you may want to consider buying a gasoline vehicle.
Gas runs smoother, fuel is easier to find, and
they are easier to start in cold weather. On the
other hand, if you plan to tow, value good fuel
economy and plan on racking up a lot of miles, then
you’ll want to buy a diesel.
Price is also an important consideration, as diesel
vehicles can be a bit more expensive than gas. If
you aren’t worried about price, then diesel may be
your best bet. For trucks, diesel is by far the
superior choice for those who like to haul heavy
loads on a frequent basis.
In passenger cars, the diesel engine has never really
caught on. During the middle to late 70s, diesel
engines in passenger cars did notice a surge in
sales due to the OPEC oil embargo, although that is
the only real significant penetration that diesel
engines have made in the market.
Although diesel engines are more efficient, there
are eight historical problems that may have held
1. Due to the higher compression ratios,
diesel engines tend be heavier than the equivalent
2. Diesel vehicles and diesel engines tend to
be more expensive than gas.
3. Because of their weight and compression
ratio, diesel engines tend to have lower RPM ranges
than gas engines. This gives diesel engines more
torque rather than higher horsepower, and this tends
to make diesel vehicles slower in terms of acceleration.
4. Diesel engines have to be fuel injected,
and in the past fuel injection was very expensive
and less reliable.
5. Diesel engines tend to produce more
smoke and smell very funny when compared to gasoline
6. They are harder to start in cold weather
and if they contain glow plugs, the diesel engines
may require you to wait before you start the
engine so that the glow plugs can heat up.
7. Diesel engines are much noisier than
gas engines and tend to vibrate quite a bit.
8. Diesel fuel is less available than gas.
Although one or two of these disadvantages would be
acceptable, a group of them is a big turn away for
Even though the list above are reasons in the past
as to why diesel never really took off, you can
expect these reasons to get corrected and improved
in the future, meaning that you will see more and
more diesel vehicles on the road.