Difference Between Diesel and Gas Powered Engines

When talking about diesel powered vehicles, the average person immediately thinks of big rigs, heavy equipment such as bobcats, bulldozers, and cranes, and so on. While these certainly are examples of vehicles that use diesel fuel, more and more everyday cars and trucks have been designed to use diesel fuel instead of standard gas. Of course, any heavy duty engine mechanic will tell you that diesel powered vehicles are second to none, but some people will still prefer to drive gasoline powered vehicles for various reasons.  Before making a decision, it would be helpful to learn not only differences but also benefits that come from diesel fuel.

Some ten years ago, diesel powered light trucks entered the market. While the concept of these vehicles was good, a number of problems kept them from reaching the level of success anticipated. A perfect example of this is the unpleasant exhaust but another problem that plagued these vehicles was the degree of noise.

In addition to these things, some of these light trucks had vibration problems and unfortunately, the cost to build one was extraordinarily high. Learning from early mistakes, diesel powered light trucks were redesigned. Although there were great advances made, a few negative factors need to be considered.

The most logical means of looking at the pros and cons of diesel fuel vehicles is to compare them to vehicles that operate on regular gasoline. For the person interested in buying a car or truck that runs on diesel fuel, going through this exercise would provide education that could then be used in making the right purchase.

Power versus Torque

To begin, we want to address power and torque as part of the comparison between diesel and gas engines. Regarding power produced, there are a lot of similarities and only a few differences. Take the amount of horsepower for instance, which in a gas powered vehicle would be greater. On the other hand, vehicles that run on diesel fuel would have a higher level of torque.

The best way to show the difference between power and torque is that when driving within the city or for short trips, a gas powered vehicle would be the better choice. However, if someone needed a vehicle with more gusto, perhaps to pull a horse trailer, boat, or camper, then torque would be needed, meaning that a vehicle that uses diesel fuel would be the wiser decision.

Another area we wanted to compare is RPM, which is the acronym for Revs Per Minute. Between the two types of vehicles, those with diesel engines produce rev that is faster, which means a higher RPM would be reached. Again, level of horsepower would be higher for gas powered vehicles while torque would be greater for vehicles that run on diesel fuel.

Now, if someone wanted to buy a vehicle with speed, something that could go from 0 to 60 without missing a beat, a vehicle that uses gasoline would win hands down over a vehicle with a diesel engine. While this might be important for some individuals, for people who have more interested in a car or truck that has the capacity to tow heavy loads such as those mentioned above, the better choice would be a diesel powered vehicle.

In addition to greater torque making it possible for loads to be pulled, this also means climbing hills and steep grades would be easier. Although the technical aspects may not be important to everyone, for someone who depends on this type of data, high compression ratio for a gas powered vehicle is 9 to 1 and for a diesel powered vehicle, 17 to 1.

In easy terms, a diesel engine produces power and torque but in RPMs that fall at the lower range. Again speaking technically, an 8.1L V8 gas engine produces 340 horsepower. This same engine would put out torque of 455 pounds per foot. In comparison, a 6.6L V8 turbo diesel engine, horsepower numbers could be as low as 400. However, 520 pounds per foot would be normal torque. Interestingly, there have been some diesel engine trucks built in the past few years capable of hitting 365 horsepower and for torque, 765 per foot.

Understanding Level of Engine Efficiency

Along with the information provided above, the engine’s efficiency would be something else to compare. Most people have faced financial challenges as a result of the most recent financial crisis so finding ways to save money is a priority. One option specific to buying a new vehicle would be sacrificing power for better gas mileage. However, most people would agree this is a sacrifice that is hard to make.

In talking about engine efficiency, the thing considered most important is BTU level. Starting with a vehicle that operates on standard gasoline, 125,000 BTUs would be produced but in comparison, a vehicle with a diesel engine would have a BTU level of 147,000. Even with this difference, the amount of power between the two would be the same. As a result, higher efficiency would be achieved with a diesel engine opposed to one that uses gas.

In addition to BTU level being important when it comes to engine efficiency, another consideration would be the actual design of the car or truck. Most people making comparisons between the two engines when shopping for a new vehicle overlook the value of design. With a gas powered vehicle, within the intake manifold gas mixes with incoming air. On the other hand, a diesel powered vehicle is designed with a fuel injection system. The difference in design is that up to 33% less fuel would be wasted or unused for a vehicle with a diesel engine.

Numerous studies have been conducted over the years and from those, detailed reports produced. Many of these reports indicate yield for miles per gallon could be as much as eight times greater for a large diesel engine truck than for a gasoline engine truck of the same size. Obviously, being able to save money on fuel is great news but for anyone who enjoys taking long road trips, the degree of savings for a diesel engine vehicle would be dramatically better.

A Look at Fuel Efficiency and Cost

All of the comparisons made so far should paint a clear picture for anyone interested in buying a new car or truck but unsure the best route to take. However, before jumping on a decision, another comparison should be made, this time for fuel efficiency and cost. The price of gas has continued to climb so getting the best possible gas mileage would be an important factor in the decision-making process.

To make this comparison, actual gas mileage between the two types of engines should be reviewed. In addition to this, the amount of money it would cost to fill the tank of a vehicle running on gasoline and one that operates on diesel fuel should be established. For fuel efficiency comparisons, combustion temperature and expansion ratio would need to be considered.

For a diesel engine vehicle, both of these are greater than what would be seen with a gas powered vehicle. For a gas engine vehicle of just one or two years of age, average efficiency rate is 24%, although when this is converted to mechanical energy, the percentage increased by 1%. For vehicles of this type, this level of efficiency is excellent but now looking at vehicles with a diesel engine, rate of efficiency increases to an impressive 30%.

Moving on to the amount of money it costs to fill the tanks of both a gas and diesel powered car or truck, people really stand up and pay attention, again because of a fluctuating economy. The truth is that it cost more to fill the tank of a vehicle with a diesel engine than one that runs on standard gasoline. Although there is a difference in fuel prices today, this was not always the case.

The bottom line regarding the price of fuel is that at the gas pump, a person would pay for more diesel fuel. However, this can be a little deceiving. Because most diesel engine vehicles are large, heavy, and have larger tanks than a car or truck driven for everyday use, the overall cost to fill the tank is significantly higher. Because of this, the relatively insignificant price difference between diesel fuel and gasoline seems to be more severe than perhaps what it is.

Looking back in time, gasoline was set with an 18.4% federal tax while tax for diesel fuel was a meager 6%. Going back seven years, a distinct pattern regarding the ups and downs for the cost of fuel can be traced.  At that time, the amount of money it took to fill the tank of a vehicle operating on gasoline was dramatically more than what a person would spend filling the tank of a vehicle with a diesel engine.

The difference we see today has to do with the way in which vehicles are being designed. As mentioned earlier in this article, along with big trucks, big rigs, and heavy equipment using diesel fuel, a wide range of conventional vehicles are being sold, also using diesel fuel.

Because of this, recouping costs by gas companies equated to coming up with innovative solutions at the pump level. Stepping up to the plate, companies came through with their plan, which means today, the price of diesel fuel is not dramatically higher priced than gasoline.

While this was and is the standard for many states, when it comes down to it, every state would set the average price for fuel. As far as the average cost of diesel fuel versus gasoline for all states, diesel is around $4.50 a gallon while gasoline sells for about $3.79.

To get to the average price a person would pay at the pump today, several factors would come into play such as fuel quality and formulas used but these have changed several times primarily due to environmental standards being established by the Environmental Protection Agency, also referred to as the EPA.

Among all the different changes that have been seen over the years, one specific one pertaining to diesel fuel has to do with sulfur levels. In 2006, accepted levels of sulfur were lowered significantly but then just one year ago, another law was put into action whereby cars and trucks operating on diesel fuel must be compliant with the rules set by the EPA.

There is yet one additional aspect of diesel fuel and gasoline comparisons that should be realized when talking about fuel efficiency. If a vehicle with a diesel engine were being properly cared for, such as having the oil changed, getting necessary tune-ups, and providing all other scheduled maintenance plus repairs, achieving 50 miles per gallon is realistic. In comparison, the most efficient gas powered vehicle on the road today only gets about 30 miles per gallon.

The 20 miles per gallon difference is huge not only for the cost of filling the tank but also the life of the vehicle. If a vehicle with a diesel engine is maintained and repaired by a qualified mechanic, having the odometer reach up to 500,000 miles is possible.  Regarding the same scenario but this time with a vehicle that uses standard gasoline, most engines would fail around 200,000 miles.

Diesel Fuel versus Gasoline – Primary Differences

Several other differences exist between these two types of engines although similarities are also shared. For instance, both a diesel and gasoline powered vehicle has internal combustion although achieving it would be distinct. For a diesel powered car or truck, compression is the main combustion method. On the other hand, combustion for a gas powered vehicle would depend on a spark lighting fuel vapor associated with direct ignition.

Something else that a person should think about is the geographic location where either type vehicle would be driven. Obviously, temperatures on the west coast are warm and dry while those on the east coast are cold and damp. Both gasoline and diesel fuel vehicles respond to climate and environment in unique ways.

For instance, in damp regions or those with climates that have extreme hot and cold changes, vehicles that use gasoline tend to struggle. The reason for this is that these vehicles do not share the same high-tension electrical ignition system design as seek with diesel powered vehicles.

If a person were to purchase a vehicle that runs on gasoline while living in a part of the country where these conditions exist, cost of repairs could quickly get high. Although even an older vehicle would cost a lot of money to keep in perfect running condition, newer cars and trucks designed with high-tech systems would be even worse.

Looking at this for vehicles that use diesel fuel, things would be different. Because a diesel powered car or truck experience less interference, complex and expensive GPS and communication systems would operate better. As shown, there are many things to consider before buying a new vehicle. Although this is one benefit, one of the primary reasons so many people are deciding to buy a diesel fuel vehicle has to do with lifespan.

Keep in mind that while some cars and trucks that run on diesel fuel reach 500,000 miles and some vehicles that use gas hit 200,000 miles, these numbers could easily change if the person were not driving responsibly or taking a lot of extensive trips, or if the vehicle were not receiving scheduled maintenance or being repaired by a qualified mechanic, among other things. In fact, top mechanics around the country agree that getting a diesel engine to last 50% longer than a gasoline engine is possible, and sometimes higher.

Good Repair and Top Safety

Having a vehicle that offers pristine performance is an important factor when comparing the two types of engines but there are other things that would be considered just as vital. The following information is something that any person should learn, whether buying a vehicle that operates on diesel fuel or one that uses conventional gasoline.

1. Again, scheduled maintenance and high quality repairs are a must, which includes proper lubrication for vehicles with a diesel engine

2.  Most people know the dangers of gasoline and fire. Vehicles that run on gas do have safety features in place but even with this, a huge explosion that would put the driver and other peoples’ lives in danger could occur with a simple spark or as the result of a gas leak. Now for a diesel powered vehicle, open air does not pose a risk of the fuel being flammable. Of course with any fuel type, potential dangers would exist but when comparing the two options, it is clear that a diesel powered vehicle would pose fewer dangers.

3.  Vapors associated with gasoline have long raised issues with professionals in the healthcare sector but also those trying to protect the environment. With this, a number of laws pertaining to emissions were created, to the point of vehicles needing to pass inspections that include standards for emissions programs. Vapors that come from diesel fuel also cause some degree of concern but on a much lower level.

4.    Regarding cooling waste heat and exhaust, typically a diesel powered vehicle would produce less

5.     Boost pressure for gas powered vehicles has pre-detonation limits while any effect connected to diesel powered vehicles would come from component strength

6.     Even the level of carbon monoxide exhaust produced by diesel engines is lower. Making vehicles operating on diesel fuel much safer than those that run on gas, diesel is the preferred choice for potentially dangerous environments to include tunnels and underground mines

7.     The last thing we wanted to address in the comparison of diesel versus gas powered vehicles has to do with cleanliness. Great concern has been raised in recent years about the depleting ozone layer and global warming. Interestingly, cars and trucks with diesel engines can be modified to run on biodiesel fuel, which is old grease that would otherwise be through away by restaurants and fast food chains.