Gas versus Diesel Powered Vehicles – Gas Mileage, Performance, and Efficiency

Typically, a person connects diesel gas with certain types of vehicles such as heavy equipment, semi-trucks, and other large vehicles. However, we now see an increase in standard cars that run on diesel gas opposed to conventional gasoline. This change is the result of many things and while a diesel powered engine might not be the right choice for everyone, it is worthwhile to understand associated benefits.

Light trucks that run on diesel gas were first introduced to the public more than a decade ago but unfortunately, these earlier vehicles presented a variety of problems. As an example, exhaust produced had a foul odor. In addition, the earlier diesel engines were known for running loud, it was expensive to build the vehicles, and in some instances, trucks vibrated. The good news is that trucks built today with diesel engines are much different although there are a few downsides to consider.

The easiest way to accomplish this is by comparing a diesel engine with a conventional gas powered engine. Learning the pros and cons specific to diesel powered engines would make it much easier to make the right type of vehicle purchase.

Engine Power and Torque

As far as power, a diesel and gas powered engine are similar but some differences do exist. For instance, level of horsepower is greater with a conventional gas engine but torque is greater for diesel engines. This is why a standard gas engine is typically the best choice when making short trips but if the vehicle would be used to pull a boat, camper, or trailer, a diesel engine would make more sense.

Additionally, diesel powered engines have a faster rev. As a result, a higher peak for “revs per minute” or RPM is achieved. Because of this, greater horsepower numbers are reached with conventional vehicles. In fact, when looking for a vehicle that can go from zero to 60 quickly, a gas engine beats out the diesel powered engine.

On the other hand, for the person who needs a vehicle capable of pulling heavy loads, torque is more important than power, making a diesel engine the best choice. Because of greater torque, diesel powered vehicles are also better at climbing steep grades. From a more technical standpoint, the ratio of high compression is 9 to 1 for a gas engine but 17 to 1 for a diesel engine.

Simply put, both power and torque are produced for a diesel powered engine in the lower range of revs per minute. Therefore, a gas powered vehicle with an 8.1L V8 engine has the ability to produce 340 horsepower and 455 pounds per foot of torque. However, a diesel 6.6L V8 turbo engine might only produce 300 horsepower but the level of torque would increase to 520 pounds per foot. Interestingly, some of the newer diesel trucks have 365 horsepower and an incredible 765 pounds of torque per foot.

Efficiency of the Engine

Efficiency is another important comparison between a diesel and gas powered engine. With such a tight economy, having the opportunity to save money is always welcomed but most people dread the thought of giving up power in a vehicle for the sake of money.

The level of BTUs in a gas engine is about 125,000 but for a diesel engine, that number is 147,000, both producing the same amount of power. The difference is that for the power wanted, more fuel would be needed to operate a gas engine. This means a diesel engine is actually more efficient when considering amount of fuel burned per gallon.

Of course, the vehicle design for both engine types would play a role in actual efficiency. As an example, gas is mixed in the intake manifold with incoming air for a conventional gas vehicle whereas a fuel injection system is used for engines that run on diesel fuel. The difference in design means unused or wasted fuel is much less for a vehicle with a diesel engine, sometimes as much as 33% less.

Reports show that on larger diesel engine trucks, yield for miles per gallon could be eight times more than for a same size truck with a gas powered engine. Of course, any savings would be appreciated but for someone who takes long trips, the degree of savings could be substantial while owning a particular vehicle

Efficiency and Cost of Fuel

Gas mileage is also something a person should consider when comparing a gas and diesel powered engine, which includes the actual cost to fill the tanks. The amount of fuel burned for a diesel powered vehicle is usually less than a gas powered vehicle.

The reason is that the combustion temperature is higher and the expansion ratio greater. Now, the efficiency rate is 24% on average for newer gas engine vehicles. As a result, conversion to mechanical energy is about 25%. While this is great, efficiency rate increases to approximately 30% for a diesel powered vehicle.

As far as the cost to fill a tank of a diesel and gas powered vehicle, an individual would pay more for diesel fuel. For many years, gas and diesel fuel cost about the same. Not only is diesel fuel higher but with these trucks typically having larger tanks, overall cost to top off a tank is much greater than for someone filling a vehicle with conventional gasoline.

Initially, federal taxation on standard gas was set at 18.4% and diesel fuel at 6%. In fact, a specific pattern for fuel costs can be traced back to 2004. Because of taxes, the cost was significantly higher to fill the tank of a gas powered vehicle opposed to one with a diesel engine. However, with so many vehicles now being built with diesel engines that the everyday person can drive, it became apparent the only way to recoup costs was for gas companies to get creative at the pump, which they did. With this, diesel fuel is not more expensive than standard gasoline.

Of course, each state is different as far as the actual cost of gasoline although $3.79 a gallon is considered average. As for diesel fuel, state differences also exist but on average, a person would expect to pay around $4.50 a gallon. In addition to changes in price, formulas and even quality of fuel has also gone through many transitions over the years. In part, this is because the Environmental Protection Agency or EPA established new environmental standards.

One change in particular was made to diesel fuel in which the content of sulfur was reduced in 2006 from 15 parts per million to just 500 parts per million. As of 2010, a law went into effect in which all vehicles powered by diesel fuel on the road had to be in compliance with the EPAs rules.

In summary, a diesel engine in pristine working order should get about 50 miles per gallon. On the other hand, a gas engine usually gets no more than 30 miles per gallon. Another huge difference between the two types of vehicles and fuel efficiency is that when maintained by a qualified mechanic, a diesel powered vehicle could get anywhere from 400,000 to 500,000 on one engine, sometimes more, while a gas powered vehicle tends to die at 200,000 miles or less.

Key Distinctions

In addition to the differences provided between a diesel and gas engine, there are a number of other distinctions. For instance, both of these engine types have internal combustion. However, achieving combustion is unique to the type of engine. For a vehicle that operates on regular gas, direct ignition is achieved when a spark lights fuel vapor while the main method for combustion in a diesel powered vehicle is with compression.

Another key distinction has to do with environment and climate. In most cases, a diesel engine would handle far better in damp environments and varying climates but because gas engines do not have the same high-tension electrical ignition system, they do not handle as well. With this ability, the cost for repair of complicated systems would be much lower with a diesel engine. This also means that a GPS and communication system would work better in a diesel powered vehicle because degree of radio frequency emission interference would be less.

Experts also agree that a diesel engine has a longer life than a conventional gas powered engine. Of course, the way a person drives, the type of driving being done, level of maintenance, and other factors would dictate the exact amount of time an engine would last, overall diesel engines last 50% and sometimes more.

Repair and Safety Factors

While performance is a critical factor when comparing the two types of engines, other factors must be accounted for. While there are many we could mention, those listed below are among the most vital.

No matter the type of vehicle a person drives, quick repairs and preventative maintenance are critical. One key issue pertaining to diesel engines is that lubrication used must be of higher quality to eliminate several potential problems.

Unfortunately, standard gasoline is extremely flammable. Therefore, an accidental spark could trigger a massive explosion, putting even a skilled mechanic’s life at risk. Even a gas leak could present a very serious risk. One of the unique factors of diesel fuel is that it does not burn when exposed to open air. Although this does not eliminate all possible risks, it certainly reduces them.

For many years, environmentalists and healthcare professionals have raised concerns about standard gasoline vapors. Because of this, a number of laws have been enacted and through emissions programs and vehicle inspections, the laws are enforced. Now, some flammable vapor is produced by diesel fuel but the amount is significantly lower.

Diesel engines also produce less exhaust and cooling waste heat in most cases

Pre-detonation limits boost pressure in a vehicle powered by a gas engine but for one with a diesel engine, any effect would come only from the strength of components

Diesel engines also produce very low carbon monoxide exhaust, making them a much safer choice for underground minds, tunnels, and other restricted environments

Finally, there are an increasing number of people that promote green living, which means making changes for a cleaner and safer planet. For instance, solar or wind power, recycling materials, and using harvested materials opposed to cutting down forests are examples of green living. Another method is by driving a vehicle with a diesel engine, capable of running on biodiesel fuel. This means a person could visit a local fast food chain or restaurant, take old grease that would otherwise be thrown out, clean it, and actually use it as fuel, something a gas powered engine cannot do.


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