Gas vs. Diesel: Which To Spec
Today’s comprehensive selection of commercial vehicle engines offers many benefits to customers. A myriad of choices enable customers to select the engine that best fits their application without sacrificing torque, fuel efficiency, horsepower and more.
While the vast engine choices create additional value, it can also create a dilemma when it comes to properly spec’ing the engine for the intended application of the vehicle. Purchasers may be overwhelmed by the selection and consequently choose an engine that doesn’t best fit the requirements. Over spec’ing and under spec’ing are common mistakes, leading to lost efficiency, productivity or a longer return on investment period.
Within the last few years, commercial vehicle manufacturers have vastly increased engine choices. The most notable additions have been diesel engines within several Class 1 light duty pickups and gasoline engines within Class 6 and Class 7 medium duty trucks. While gasoline engines still dominate Class 1 and diesel engines make up the majority of Class 6 and Class 7, these new engine choices make the decision much more analytical than ever before.
So how do you know which engine is right for the job? There are many factors to consider as it pertains to the engine when in the market for a new commercial vehicle.
Commercial vehicles would all be perfect if cost didn’t need to be factored into the equation. Unfortunately, the real world operates on financial constraints so unlimited funding for your next work truck just isn’t feasible. That being said, cost is a major influencer on the selection of the commercial vehicle, especially as it relates to the engine.
Acquisition costs can be substantially higher with diesel engines, stretching from $8,000 more in light duty commercial vehicles up to $12,000* in heavy duty commercial trucks. Gasoline engines offer the advantage with significantly lower acquisition costs.
Horsepower & Torque
Selecting an engine with enough horsepower and torque is vital for success with many commercial vehicles. The most common application considered for ample horsepower and torque is pulling a trailer, regardless of size. The more weight on the trailer, the more important horsepower and torque becomes. Other applications, including hauling bulk material, should also pay close attention to the horsepower and torque ratings of an engine as these vehicles are consistently hauling the maximum available payload.
While gasoline and diesel engines have similar horsepower ratings, they are vastly different with torque. Looking at a class 3 pickup, the diesel has a slight advantage in horsepower rating yet boasts a torque rating two times that of the gas engine**. Point being, if you are towing heavy loads or your application relies upon torque to get you moving a diesel will be the better fit for you.
Federal regulations have forced commercial vehicle manufacturers to maximize fuel efficiency within new vehicles, regardless if they contain diesel or gasoline engines. This has caused the gap of fuel efficiency between gasoline and diesel engines to shrink. Historically, diesel engines have held the advantage of fuel efficiency over gasoline engines. Today, you can expect a slight difference between most gasoline and diesel engine choices. For instance, with a light duty Class 1 pickup you can expect to see a combined fuel efficiency rating of 20 mpg with the gasoline engine and a combined fuel efficiency rating of 23 mpg with the diesel engine***.
Commercial vehicle customers should compare the price per gallon of diesel and unleaded fuel and factor in projected annual mileage to determine overall fuel costs.
Snowplows, dumps, cranes, many different applications require a power-take-off (PTO). To avoid potential compatibility issues, ensure the engine (and transmission) you select will allow for PTO installation. Many truck manufacturers offer a “PTO prep” option, making the installation of the PTO unit more seamless for the upfitter.
At one time, your only choice for PTO compatible engines were diesels. Today, many manufacturers offer gas engines that can easily accommodate a PTO unit for auxiliary equipment.
Engine idling is common within many vocations that employ commercial vehicles to get the job done. Today, many local and state regulations are in place to discourage companies from engine idling. This has led to many product developments, including stand-alone, mobile power systems that mount on the commercial vehicle. For companies that are still allowed to idle their engines on the job, there are obvious benefits associated with diesel engines.
Diesel engines idle at a lower speed and are engineered for severe duty cycles, making them the more popular choice within high-idle applications.
The longer the life cycle of the vehicle, the more vital engine maintenance will become. There are many considerations to be made as it pertains to maintenance including cost of replacement parts, preventative maintenance intervals, qualified technicians, warranty coverage and more.
While diesels have longer maintenance intervals and warranty coverage, there are additional components and requirements (DEF fluid) that aren’t found on gasoline engines. Diesel replacement parts tend to be more expensive and finding qualified diesel mechanics can be a challenge in certain geographic areas.
Cost leans heavily towards gasoline while torque, engine life, fuel efficiency and idle frequency favors diesel. PTO provisions and maintenance are heavily reliant upon the application. As always, be sure to have a clear understanding of the intended application of the vehicle to help ensure you make the best selection for the job at hand.
*Comparing 2016 Ford F-250 gas(6.2L) and diesel (6.7L) pickup for light duty and 2017 Ford F-750 gas (6.8L) and diesel (6.7L) cab chassis for heavy duty, prices are MSRP from ford.com.
**Comparing 2016 3500HD pickup with Vortec 6.0L V8 gas engine rated at 360 horsepower and 380 ft-lb. of torque and Duramax 6.6L V8 diesel engine rated at 397 horsepower and 765 ft-lb. of torque
***Comparing 2016 Ram 1500 2wd with a 3.6L gas engine with 2016 Ram 1500 2wd with a 3.0L diesel engine, both models with 8 speed automatic transmission. Data obtained from National Highway Traffic Safety Administration (nhtsa.gov).