Better durability, increased fuel economy, more opportunity for future development, less major maintenance...does this sound like something you look for when buying a car? Well luckily these are all characteristics of a diesel engine. Technology has completely transformed diesel engines from the clunky, old, black smoke emitting engines that many of us picture in our minds. Diesel has come a long way, yet remains to be very young in its development. As an engine that creates more energy out of every single drop of fuel, its potential in our ever-growing world is huge! Although for decades diesel has been widely rejected in America, it has recently become increasingly accepted. "Clean diesels" and "ecoDiesels" are being sold and released by auto manufacturers at growing rates in America. This growth is noteworthy and I will explain why by examining the layers behind the surface, explaining how and why this change is taking place, using tactics like history and developments of both engines. Having spent years working as a mechanic on both types of engines in a commercial setting, I have witnessed developments on both sides of the equation, and I will use my experience to provide a better understanding of the internals of each engine and fuel that creates the distinct characteristics of the engine, and in turn, the feelings of the car that you drive, such as speed, acceleration, vibrations, and noise. I will examine all relative aspects of both engines, and I will illustrate why diesel is the overall "better" engine, through fuel economy and other statistics. 

For years, one of the biggest controversies in many industries has been what type of fuel to use. Whether it be a grill to cook food on, a car, truck, boat, or power for an entire city, we struggle to settle on one type of fuel. The reasons for this vary, as each fuel has its pros and cons, and certain places are more suitable for certain types. For example, a semi truck would prosper from having a diesel engine, whereas a racecar would benefit from a gasoline, or even electric engine. This remains true in the American auto industry, where consumers and automakers alike have struggled with the question of whether they should build and sell, or buy and drive, a gasoline or diesel powered vehicle. This has been a controversial subject for many years, and while diesel has proved to be the answer in many European cities, it never took off in American small cars like it did in Europe. America did give diesel cars a try during a fuel crisis caused by the OPEC oil embargo of 1973 that led to gasoline shortages (Smith). This effort failed, mostly due to primitive technology. The Oldsmobile Diesel is the epitome of diesel failure during this period according to J.C. Smith who stated "The Olds Diesel was unrefined, leaving a cacophony of clatter and rattle in its wake.  It emitted a foul, tractor-trailer-like smell.  So, when you weren't renting a car while Mr. Goodwrench further maimed your engine, you got to drive a loud, stinky and laboriously slow car.  Mark of Excellence?  Not so much (Smith)." Smith's example represents a lot of stereotypes surrounding diesel cars, but with today's technology many of these are no longer relevant. This essay will go into depth on the question of Which is better? Gas or Diesel Engines? I answer this question by examining the history of both types of engines, the pros and cons, their uses and markets, and where the future lies for each. The primary stakeholders in this argument are people who are deciding between a gas or diesel car model. The manufacturers of these car models also hold stakes because their company must produce what the public wants, or make the public want the car that they are producing. I believe diesel engines are the way to go, that diesel is the engine and the fuel of the future, and will explain why in the following pages. 

One of the most important factors involved in purchasing a car is the financial cost. Regardless of who buys the car, whether it be a millionaire buying a brand new Ferrari or the average joe buying a used clunker. The buyer is going to take purchase cost, maintenance costs, depreciation, and operating costs such as what type of fuel it takes and how efficiently it uses that fuel. In all of these costs I mention, less is almost always better. In general, Humans hate overpaying! Modern diesel powered cars are a better financial choice because of these factors. According to Forbes, a diesel powered vehicle costs $5045 more on average than a gasoline powered vehicle. However, when comparing a diesel VW Jetta TDI vs. a gasoline powered Jetta, the price difference is $2,100. In the same comparison by edmunds, they found the diesel returned 34 miles per gallon compared the 28 miles per gallon from the gasoline powered equivalent. These figures lead to a $9.96 fuel savings average across the Nation, but in some states savings were as high as $253.96 annually (Edmunds). That comparison also states that a real world VW TDI test vehicle returned an even higher MPG of 37.8, and that with current fuel prices, the extra initial purchase cost of the diesel option is offset by fuel savings in 8 years, or 124 thousand miles driven. Therefore, depending on where you live, a modern diesel car can prove to be a better long term investment, and make more sense economically.

One of the most unique characteristics that sets the diesel engine ahead of the gasoline engine is the torque it can produce. The Merriam-Webster dictionary defines torque as: "a force that produces or tends to produce rotation or torsion ... ; a measure of the effectiveness of such a force that consists of the product of the force and the perpendicular distance from the centerline of action of the force to the axis of rotation (Merriam-Webster)."  Basically, torque is what gets a vehicle going or accelerates it initially, especially when under load, while horsepower is what accelerates a vehicle under motion. Banks is a company which specializes in performance of all types of engines, they even build the engines for Navy SEAL covert action boats, which shows their credibility. Banks experiment between a similarly modified diesel and gas motor illustrates the amazing torque diesels produce."The Banks Project Sidewinder, a Dodge Dakota pickup fitted with a modified Cummins 5.9L (359-cubic-inch) in-line six-cylinder diesel, made 1300 lb.-ft. of torque during its record-setting Bonneville Salt Flat runs at 222 MPH. That's not a misprint - we'll repeat, 1300 lb.-ft. of torque! That's over 220 lb.-ft. per liter." This experiment by "Banks", one of the leading turbo manufacturers in the diesel business, found by comparing 2 similar performance engines, one diesel and one gas, that the diesel produced 1300 ft/lbs of torque, compared to the gasoline engine's 775 ft/lbs of torque.  While this is an extreme example, and does not apply much to the everyday driver, the idea holds true throughout all applications of the engines. A 1985 VW Golf Diesel was rated at 98 ft/lbs of torque, versus the 72 ft/lbs of torque the same car produced with the gasoline option (VW Motors). These statistics become tangible once behind the wheel, imagine going up a hill with your foot down on the pedal, a gasoline engine will be working harder at higher rpms, and burning more fuel during this time than a diesel engine. In addition, the mechanics of a diesel engine are inherently more suitable for lower rpms. This means that the previous scenario will hold true whether you are going up a steep hill, or cruising down the highway on a road trip. Diesel engines are constructed with longer crankshafts, which naturally produces more torque. The tradeoff to this construction, while not necessarily a downfall, is that it essentially governs the engine, meaning the engine can only physically reach a certain amount of RPMS. While all engines are somewhat limited by this, diesel engines experience it at a much lower RPM, which is a side effect of their amazing torque abilities. 

Another amazing characteristic of diesel engines that results from their mechanical construction is their fuel efficiency. The lower RPMS of the engine, and the chemistry of the fuel work together to form a very fuel and energy efficient combustion process. A study by consumer reports showed that the 2012 Chevrolet Cruze turbo diesel returned a remarkable 49 MPG on the highway, this is solely due to its efficient power plant, fueled by diesel. The same study showed that diesel powered cars are overall about 30% more fuel efficient than gas. Diesel fuel is comprised of longer carbon chains, which in turn leads to a slower burning fuel, and more energy contained in a single drop compared to gasoline. To be exact, diesel fuel contains 11% more energy per gallon than gasoline. In fact, the black smoke you may have seen a diesel truck spewing out its exhaust pipe is actually unburnt diesel fuel! That shows how slow burning the fuel is, and while it is a negative effect, harnessing 100% of that combustion would result in even more efficient engines. This slow burning fuel, combined with a slower turning engine results in less fuel being used to go the same distance as a gas counterpart. 

Owning a diesel will decrease your trips to the fuel pump. However, one of the biggest downsides to owning a diesel powered vehicle is the cost and availability of fuel. Although they are more fuel efficient and can go further on a single tank of gas, the cost per gallon of diesel fuel in the United States is well above that of any type of unleaded gasoline. Diesel fuel is currently taxed at 24.4 cents per gallon, while gasoline is taxed at 18.4 cents per gallon (NACS). These taxes are due to transportation reforms that started with Ronald Reagan in the 80's and have stuck around to the present day (NACS). The reforms were brought about in order to improve our highways and infrastructure, and were meant to tax the trucking industry, who heavily rely on diesel for their trucks, which cause more damage to roads than passenger vehicles. However, these taxes now negatively impact anyone who owns a diesel, and take away some of the appeal of owning one. In addition to the higher price of diesel fuel, it is less prevalent at US gas stations. In fact only about 50% of gas stations in the US report they carry and distribute diesel fuel (Voelcker). The fact that 98% of American passenger cars are fueled by gasoline and not diesel explains the reason for the scarcity of diesel pumps (NACS). However, a quote from John Voelcker shows this diesel fuel scarcity is currently changing. Voelcker states: "U.S. clean diesel vehicle sales increased 25.6% in 2012, almost double the overall auto market's increase. More diesel-powered vehicles mean more demand for diesel fuel. Comparing October 2010 demand to that of October 2012, demand for gasoline has decreased 3.4% while demand for on-road diesel fuel has increased 11.8% (Voelcker)."  This is good news for anyone interested in buying a diesel, because not only will diesel fuel be more convenient and easier to find, it will also increase the supply and drop the demand, resulting in lower prices.

Diesels have long been known as high polluting vehicles. You have most likely seen an old dump truck spewing thick black smoke into the atmosphere, and this is where the stereotypes stem from. This stereotype is no longer valid, as most clean diesels emit less carbon dioxide than gasoline engines. However this "cleanliness" comes with a cost. In order to meet the strict emissions standards, many modern diesels have a urea injection system in their exhaust systems. This system neutralizes sulfur and other pollutants before they exit the exhaust system, and upon exit results in an undetectable difference in smell between a diesel and gas car. More importantly, this system results in much cleaner exhaust gases being released in our atmosphere. This system is great for making "clean diesels" but it comes with an inconvenient cost that gas powered vehicle owners can forget about. Modern clean diesels with this system have an additional reservoir to hold this urea solution. The urea solution is commonly known as AdBlue or DEF (Diesel Exhaust Fluid). The reservoir is usually near the gas cap, and it requires periodic maintenance-checks and refilling. This can be a large inconvenience for a busy person who wants as least maintenance as possible, and can be a main reason to stay away from diesels. In addition to the inconvenience of refilling the system, it is also an additional cost. According to Cars.com, the cost for one gallon of AdBlue at a parts store is $7.50 per gallon, the VW TDI holds about 5 gallons, and needs to be refilled every 10,000 miles (Popely). Assuming you replace the fluid yourself, you are looking at an extra $50 every 10,000 miles you drive, or even more if you have a shop do the job. This is a huge con to the clean diesels currently on the market, and gives gas engines an extra point on the tally board! Another additional downside of buying a diesel is that brand new, they typically cost more than gas models. While this cost can be considered an investment due to the fact it is normally gained back in fuel savings, it can be a downside to anyone looking for a low initial purchase price. 

The diesel engine has been around since the 1890's, and was invented by Rudolf Diesel. The first engines were restricted to extremely low operating speeds due to their size and injection systems. Since then, much has changed, diesel engines have grown lighter, faster, smaller, and more efficient. This has allowed diesel engines to evolve from a generally unrealistic motor in terms of general public use, to a motor that we can all benefit from. Many stereotypes surround the diesel engine, they are known for being noisy, stinky, loud, heavy, and generally clunky. These were all once true, and still remain true in some applications of the diesel engine, such as generators, semi trucks, and most older diesel vehicles. However, technology has transformed the diesel engine, and modern diesel car engines refute every single one of these claims. A huge landmark in all types of engines was forced induction, in the forms of turbochargers and superchargers, but this new type of induction especially revolutionized the diesel engine. Induction is the process of pulling air into the engine cylinder for combustion, and by forcing more air in via a turbocharger, one can create more power using the same amount of energy. For the diesel motor, this changed it from being a heavy, slow, and inefficient machine, to a quick, powerful, and very efficient machine. Turbochargers are becoming the "go-to" for applications of both performance and efficiency, and diesel engines can handle the extra pressure substantially better than gasoline engines. This pressure is calculated in PSI, and is known as "boost pressure". 15 PSI is A LOT of boost for a gasoline engine to handle, and can cause premature wear on engine parts due to the added pressure. Contrarily, an average turbo diesel engine runs on about 30-50 Psi of boost pressure, and faces none of the negative wear and tear associated with turbo systems on gasoline engines (Banks). The reason for this is the rugged construction of diesel engines, they are built with heavier, more robust parts to withstand this type of scenario, and this in turns lead to a more durable engine. 

Our world is constantly evolving, and modern technology is quickly increasing the rate at which all aspects of our world are growing. Machines of all type are becoming more efficient, robots are replacing humans for reasons of cost and efficiency. For these same reasons, diesel engines will take off. I believe we are still at the beginning of developing all engines, however I see huge potential in diesel engines. Ongoing studies such as the one conducted by Wang Xioyong, which can be found in my sources, have shown the plausibility of diesel and compressed air hybrid engines. Imagine driving a car powered in part by the very air we breathe. This is the potential we need to draw awareness to, and this potential excites me. Since the late 1800's, when the first of both gas and diesel engines were invented, the diesel engine has seen far more drastic developments, and I predict we have only scratched the surface. In fact, for the first 40 years after diesel fuel was discovered, it was thrown away as a "waste product" of refinement for petroleum products. This ignorance is not acceptable in our world of limited resources, and we cannot afford to overlook very good alternatives to our beloved gasoline engine. Diesel engines are making their way into mainstream America, this support and knowledge will continue to fuel mechanics, scientists, and inventors for many years, and it is important for us to remain vigilant of the changes and progress that is occurring. 

