In this article I'm going to discuss the properties of the diesel and gas engines, and compare them to each other. I'm specifically referring to their use in automobiles.

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 movement of the piston is then transferred to the wheels through crankshaft, gearbox and transmission.

It's when we look at the engines a little closer that we start to notice that there are differences. Differences in gas mileage, smell, vibrations, price and expected age to name a few.

The gas engine has an ignition system with high voltages, wiring and spark plugs. The diesel does not need this, it compresses the fuel/air mixture until it's so hot it ignites all by itself. 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 and is burned the next time the piston passes the compression stage.

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. Fully compressed the air is hot enough to ignite disesel and at that point high pressure nozzles will start to spray fuel into the cylinder. The high temperature of the cylinder instantly ignites the fuel.

The differences is fuel injection and ignition results in the diesel burning the fuel more efficiently than the gas engine. 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. If it's cold enough outside the air will not become hot enough and it will not ignite the fuel, then the engine will not start.

That's why diesels have glow plugs that are used when starting a cold engine. Electricity from the accumulator heats the glow plugs inside the cylinders before you even try to start the engne. This way the hot glow plugs ignite the fuel when the air is not hot enough to do it. Then when the engine starts it only takes a few seconds for the cylinders to get hot enough to ignite the fuel without help and the glow plugs are not needed again until the next cold start.

This is one of the things that might bother you when having a diesel engine in the car. Glowing can take from a couple of second to half a minute and can be quite a stress if in a hurry. You just have to wait until it's finished or the car won't start. On a modern engine the glowing does not take long, it might not even be required, and you'll 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. In addition it has a more robust construction because of the high compression is must handle and can usually go twice as many miles as the same size gas engine during it's life. The heavy duty contruction also makes it expensive when bought new.

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)
• Top speed is nothing to brag about but there should be no problem maintaining the speed limit in most places
• Glow plugs helps ignite the fuel when the engine is really cold
• Clean air is sucked into the cylinder, then fuel oil is injected
• Engine is simple and robust. Costs more but will run many miles
• Emits black smoke when loading it (like a quick acceleration)
• Can be converted to run on Eco fuel oils
• Has better MPG than a gas engine

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.