Diesel Cars vs. Standard Gasoline Vehicles: A Comparison Guide

February 27, 2012

Compare the advantages of diesel cars over gasoline car, and learn 5 ways to increase diesel car fuel economy.

Refuelling A Diesel Car

Gasoline engine and diesel cars work on the same principle, the process of internal combustion. This means they convert the energy of burning fuel into power to move the pistons. Both engines make this energy through small explosions in the combustion chamber. However, this is where the similarities end.

Fuel Ignition
In a gas engine, the gas is mixed with air and compressed by a piston. This is then ignited by a spark from the spark plug. The explosion forces the piston out, which starts the cycle all over again. In a diesel engine, this process is a little different. The air is compressed first and then the diesel is injected into it. As the air is compressed it heats up, causing the diesel to explode. There are no spark plugs in a diesel engine.

As a gas engine runs, it emits exhaust to get rid of burnt gasses produced by the combustion process. Because the gas and air is mixed before it is combusted, there is a lot of residue left. If the engine is not tuned just right, you also use a lot of excess gas in the mixture. This causes less efficiency at the gas pump. Because the diesel fuel is injected directly into the cylinder, there is less waste, causing the engine to run cleaner.

Injection Process
The injection process of both engines is also different. With a gas engine, the injection is done through a carburetor or a port injection of some sort. This means that all the gas and air is loaded into the cylinder before anything starts to be compressed. This combination limits the amount of compression that can happen. If the mixture is off a little, it can cause knocking in the engine and eventually damage the cylinders. A diesel engine does not have a carburetor. It injects the diesel directly into the cylinder after the air has been compressed.

Cost to Run
The diesel engine creates more energy than a gas engine. This is the major reason why so many large vehicles run on diesel fuel. One gallon of diesel generates 147,000 BTUs, while one gallon of gas gives off about 125,000 BTUs. This extra energy produces more power while using less fuel in the process.

Green Concerns
One of the problems with diesel engines is that they emit a sort of soot that can lead to acid rain. They are not as heavy as carbon monoxide and other greenhouse gases like a gas engine, but a diesel engine does give off some harmful emissions. To combat this, a diesel engine can use an additive known as biodiesel. Biodiesel is not made from petroleum but from plant and animal oils. It can be added directly to the diesel engine without any modifications. This is unlike driving a hybrid vehicle, or having to modify an engine to use alternative gases. This reduces the harmful emissions, but it reduces the efficiency, as biodiesel does not burn as well as petroleum diesel.

4 Reasons to Buy a Diesel Car

Diesel cars seem to have a negative connotation to them due to past thoughts on the subject. However, with advanced technologies, the problems of diesel engines have almost all been eliminated. Diesel engines used to be thought of as noisy and smelly, with dirty emissions. There have been great strides to improve the pollution, although they are not quite there yet. What was really fixed was the noise aspect, and they are practically just as quiet as gasoline engines. Diesel cars are more popular in Europe since there are lower fuel emissions standards, but in 42 out of 50 states, diesel cars are allowed, and gaining popularity. Here are some diesel advantages and reasons to buy a diesel car.

Fuel Economy
One of the biggest reasons people consider buying a diesel car is the fuel economy. Diesel engines are much more efficient than gasoline engines. Diesel fuel economy compared to gasoline is about 33 percent better. This means that you end up filling up your tank fewer times since you are getting more miles to the gallon. Many European diesel cars get 40, or even 50 miles to the gallon on the highway. Diesel fuel is usually priced at, or a little bit above the price of regular gasoline. Biodiesel is even more expensive, but is not readily available at many gas stations. Still, he price of diesel is not 33 percent higher than gasoline, so the cost benefits to diesel outweigh gasoline.

Engine Power
The engine in a diesel car is not only more efficient, but more powerful. Diesel engines are usually V6 engines with many more horsepower. Coupled with that, diesel engines produce more foot pounds of torque for better acceleration. Diesel engines do cost a bit more than gasoline engines, so a diesel model may be priced a thousand or two thousand dollars higher, but the gas savings can make up that cost very quickly. These engines are also very long lasting. It is not uncommon to see diesel cars run for over 200,000 miles. Many people buy them for the fuel savings, and the more miles you can get out of the engine, the more gasoline savings you can achieve.

Residual Value
Diesel cars hold their value more so than gasoline cars. If you own a diesel car, when you are getting ready to sell it the value will be several hundred dollars higher than its gas powered equivalent.

Driving Performance
The typical diesel powered car does not reach high speeds quickly. The high energy potential provided by the diesel fuel itself makes the car more dependable, but less responsive.

Diesel Car Fuel Economy Tips

Owning a diesel car will automatically give you a savings in gas. While the current diesel fuel prices may be a little more than regular gas, you still save money. A diesel engine uses up to 1/3 less gas per mile than a car running regular unleaded gasoline. This savings can add up a great deal. However, to increase your diesel MPG, you can follow the general rules of saving gas with an unleaded vehicle. Here are some of the things you can do to save money with a diesel car.

Drive Slower
The biggest diesel saver is the same as that of a regular unleaded vehicle: drive slower. More speed means that more power is being generated by the engine. This power comes from the use of more diesel. Simply slowing down a few miles an hour will give you a tremendous savings at the end of the year. For highway driving, keeping your speeds at the posted limit can save you up to 20 percent more diesel.

Keep Air Conditioning Off
It is common knowledge that the air conditioner uses a lot of power in your car. Every time that the unit is turned on, power is diverted to the compressor to send the cold air through the car. To compensate for the power that was lost, the diesel engine has to work much harder to keep speed up. This means that more diesel is used to keep the power from the engine constant. Turn the air conditioner off for better diesel MPG.

Stay in Constant Motion
The more you can keep your vehicle moving without having to stop, the more diesel you'll save. If you have to drive in congested traffic, or have to start and stop a lot, you're using a lot more diesel than if you just continued driving. Seek out alternate routes on your way to work, to shops or for general errands to help you conserve a great deal of diesel fuel and save money in the process.

Reduce Weight
The heavier your vehicle is, the more your engine has to work in order to move it. If you have a pickup or a cargo vehicle, you will see a drastic difference in gas consumption. Keeping your diesel car empty of anything that will unnecessarily weight it down will help you save money on diesel fuel prices.

Keep Engine Tuned
When you let your engine go for long periods of time without any service, you eventually begin burning more diesel. While these engines require less service, you should always perform regular maintenance. This will keep your engine parts well lubricated and clean for better performance.

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