A standard internal combustion engine features either diesel or gas as its source of fuel. The two vary mainly in their ideal applications and the ways in which they function, which ultimately influences their life expectancy. In this article, you will learn about gas and diesel engine operation, maintenance and repair considerations, and finally diesel vs gas life expectancy.
Diesel vs. Gas Engine Operation
Diesel and gas engines are both internal combustion engines, which means through a series of chemical processes including combustion, the engine is able to produce kinetic energy. For both types of engines, fuel in the piston cylinder assembly is combined with air and combusted. This internal combustion inside the piston cylinder assembly forces the piston up and down which in turn creates rotary motion in the crank shaft that the pistons are attached to. Through the proper timing, all the cylinders in an internal combustion engine work together to create seamless rotary motion in the crank shaft.
The main difference between a diesel engine and a gas powered engine is the way in which the combustion occurs.
In gas engines, the fuel is combined with air and then compressed by the piston head and ignited with a spark plug to combust the fuel and force the piston back down. This process is is outlined by the four stroke combustion cycle. The initial stroke is the intake stroke where air is pulled into the cylinder, followed by the compression stroke where the air is compressed and fuel is injected and ignited causing combustion. The combustion leads to the power stroke where the piston is forced down from the combustion and rotates the crank shaft. Lastly, the exhaust stroke resets the cycle bringing the piston to the top of the cylinder and releasing exhaust gasses through the exhaust valves.
In a diesel engine, a similar four stroke cycle is followed with a couple major changes. In the compression stage air is compressed before the fuel is added and through a process called auto ignition, the diesel fuel combusts due to the high temperature of the compressed air in the cylinder without the need of a spark. Glow plugs replace spark plugs in diesel engines and are only used for the initial combustion.
Maintenance and Repair
When it comes to maintenance, gas engines are typically cheaper to maintain and repair than their diesel counterpart. Gas engines typically have much smaller components than diesel engines requiring much less lubrication or in the case of engines, oil. Due to the amount of oil needed and that is being used for the lower torque application of diesel engines, the maintenance costs will add up. Other than oil, the spark plugs in a gas engines should be replaced about every 50,000 miles to ensure proper combustion where as glow plugs may be replaced every 100,000 miles.
In terms of the lifespan of the engines, the replaceable liner in a diesel engine allows for maintenance and repair beyond tune ups and lubrication. In terms of general maintenance and repair, gas engines are cheaper- however longevity is definitely far better from a diesel engine.
In larger more industrial applications, gas engines and diesel engines used in power generation typically require larger scaled and more frequent maintenance checks. Ensuring proper combustion, lubrication, and fuel levels are the major priorities in keeping a large combustion engine healthy. Similarly, being mindful of ideal operating temperatures and other environmental factors are important considerations to make when operating the industrial grade engine for the longer term applications.
Diesel vs. Gas Engine Applications and Life Expectancy
Diesel engines and gas engines vary especially in their applications. Typically speaking, diesel engines are more suited for low RPM and high torque applications, meaning they are ideal for towing and moving heavy loads. For this reason, a lot of heavy duty trucks come equipped with diesel engine for their towing capabilities. On the other hand, gas engines are ideal for higher RPM and low torque applications which covers most other type of vehicles, which accounts for most consumer commuter vehicles.
Because of their heavy duty applications, diesel engines are designed with removable cylinder liners that may be replaced every couple hundred thousand miles that may be replaced. For gas engines, the effects of wear are far less replaceable as there isn’t a removable liner in the cylinder assembly. Because of this diesel engines are known to last far longer than their gas counterpart.
Other applications of diesel and gas engines are typically found in the area of power generation. Larger scale diesel and gas engines may be used for large scale electricity generation. Typically for shorter and smaller applications of power generation such as in residential areas, gas engine generators are the ideal choice as they offer quick power for short amounts of time and are usually cheaper than their diesel counterpart. However, if long term idling and power generation is required, diesel generators are ideal as they are far more robust and useful for longer-term applications.
External factors come into play when choosing between diesel and gas engines such as temperature. Due to the absence of spark plugs, starting a diesel engine in colder weather used to be a major concern, but with the introduction of glow plugs, preheating the engine to operate properly has increased the robustness of the diesel engine. Gas engines use spark plugs for combustion, making temperature less of a concern.
Other uses for diesel and gas engines include construction, mining, forestry, and agricultural applications.
When considering the low rpm applications of the diesel engine, it means that it cranks far less than the gas counterpart which also attributes to the diesel engines larger life span. Typical gas engines will become heavily worn past 120,000 miles where as diesel engines experience similar wear at closer to 300,000 miles.