Gas Engines vs Diesel Engines

Curious just who’s using the green pump at the gas station? Wondering why your gas tank has the warning “unleaded fuel only”? Today we’ll break down the differences between gas and diesel engines, lay out the pros and cons of both, and leave you with a lot more knowledge to help your future car purchasing decisions.

Both cars that run on unleaded fuel and those that run on diesel use an internal combustion engine – one that takes in air and fuel, causes an explosion in a small space, and powers the car – so what’s the difference?

How Does Fuel Get Into The Cylinders?
In some gas engines, fuel gets into the engine using port injection, fuel is injected right before the intake stroke. Other gas engines use a carburetor to mix air and fuel before entering the cylinder. There is no direct injection of fuel.

Diesel engines, however, use direct fuel injection. Fuel is injected right into the cylinder making it, arguably, the most important part of a diesel engine.

What Starts Combustion?
The other difference is what causes the combustion – the explosion that creates gases that power motion in the engine. Gas engines rely on meticulously timed spark plugs to continuously spark at the right second during compression. Diesel engines don’t use spark plugs. Instead, the engine relies on a high enough temperature internally to ignite the gas. Compression causes the air temperature to rise in each cylinder, causing combustion in each.

Different Fuels, Both With Pros and Cons
Both gas and diesel fuel are made from petroleum but manufactured differently depending on their purpose.

Just looking at the two shows big differences, namely that diesel is heavier. In scent, in weight – diesel is oily and evaporates more slowly than gas.

Besides the appearance, though, the two are different on an atomic level. Diesel, which is less refined, provides more energy than an equivalent amount of gasoline. This is why it gets better mileage. The downside, though, comes with the after effects of burning diesel. While a cursory look at diesel emissions show it doesn’t emit as many greenhouse gases as gasoline, it does emit high amounts of nitrogen and soot – which get trapped in the water cycle, are a factor in smog, and can impact air quality.

As more of a focus is placed on environmental matters and vehicles, engines and fuel are redesigned to reduce their negative impact, we may see more vehicles use diesel.

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