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In this article I’m going to discuss the properties of the diesel and gas engines, and compare them to each other. Specifically their usage in cars.

Looking at them from a distance both the gas and the diesel engine work in about the same way. Fuel manufactured from refined crude burns in the cylinder forcing the piston to move from the resulting pressure. The motion of the piston is transferred to the wheels through the crankshaft, the gearbox and through the transmission.

It’s when we look at the engines a little closer that we start to notice that there are differences. Difference in fuel economy, smell, vibration, expected age and price just to name a few.

The gas engine has an ignition system with high voltages, wiring and spark plugs. This is not needed in a diesel as it compresses the air n the cylinder until it’s hot enough to ignite the fuel when injected. In a gas engine the spark plug ignites the fuel/air mixture by sending a high voltage spark into it at the right time.

Another thing that separates the diesel from the gas engine is that gas engines adds the fuel vapor to the air in the intake manifold either through a carburetor or through fuel injection nozzles. The air/fuel mixture is then sucked into the cylinder to be burnt the next time the piston strikes.

The diesel on the other hand sucks clean air into the cylinder and then waits for the piston to compress the air as much as it will go. At this time when the air is compressed and hot enough to ignite the fuel, diesel is injected directly into the cylinder (or a small space connected to the cylinder) through high pressure nozzles. The fuel ignites instantly due to the high temperature in the cylinder.

The different fuel injection and combustion lets the diesel work more efficiently than a gasoline burner. That’s why a diesel has a better gas mileage than it’s gas powered counterpart.

This is not to say that a diesel is better. It’s different, it has drawbacks too. Diesel engines usually is harder to start in cold and freezing weather. If you remember it was compressed hot air that ignited the fuel. When it’s too cold outside the air will never become hot enough to ignite the fuel, and the engine won’t run.

To handle this diesels have something called glow plugs for handling cold start situations. Electrical power from the accumulator is used to preheat the glow plugs inside the cylinders before the engine is started. This way the hot glow plugs ignite the fuel when the air is not hot enough to do it. A couple of seconds after the engine has started it is usually hot enough to ignite the fuel without the help of the glow plugs and these are not used again until the next cold start.

This is one of the things that might bother you when having a diesel engine in the car. The glowing takes from a couple of second to half a minute and can easily lead to stress when in a hurry. You just have to wait until it’s ready or the car won’t start. On the other hand if the engine is well done the glowing does not take long and you soon get accustomed to it.

Lets for a second look at the practical differences between the diesel and the gas engine. The diesel engine is large and loud and it produces clouds of black strinking smoke when accelerating. It also has a sturdier construction due to the higher pressures it must handle and thus can often go twice as many miles as a gas engine during it’s lifetime. The sturdier construction also makes it more expensive when first bought.

The Gas Engine

• More quiet that the diesel
• Better acceleration and higher top speed
• Uses an Ignition System with Spark Plugs to Light The Fuel
• Adds fuel to the air before letting it into the cylinder
• Not as sturdy as a diesel. Lower price but breaks down faster
• Gas readily available everywhere
• MPG is low compared to a diesel

Features of The Diesel Engine

• The diesel engine is loud and has the sound of an agricultural machine or an 18 wheeler
• Slow acceleration (get one with turbo charger, that helps)
• Moderate top speeds but can easily reach the legal speed limit in most places
• Glow plugs helps ignite the fuel when the engine is really cold
• Lets clean air into the cylinder and injects the fuel later
• Engine is simple and robust. High price tag but can run many miles
• Emits black smoke when loading it (like a quick acceleration)
• Easy to convert to using Eco fuel oils
• Has a great gas mileage

If I where to give you advice on selecting either a gas or a diesel powered car I would tell you this: Get a diesel if you drive long trips and can live with the small nuisances of more noise and poor acceleration. Get a gas powered car if you drive less than average or if you just want the comfort at any price.