Many times you can look at what the large companies are doing and follow in their footsteps. However, when it comes to choosing between gasoline and diesel engines to move your fleet, playing follow the leader could cost your small company more money. That’s because each fleet manager has to incorporate the variables of cost expenditure to determine the best fuel/engine platform for their fleet.
Consider some of these comparisons in your decision and you may save your company dollars when the numbers are crunched.
Initial Purchase/Lease – Purchasing a vehicle or leasing is different article all together. The variable here is the cost of power platform. A diesel engine normally costs between 8-13% higher over it’s gasoline counterpart. That’s due the complexity, technology, and additional components diesel engines must have to meet today’s EPA requirements. It’s also important to compare the horsepower needed for your application. For most urban areas, a 4 or 6-cylinder gasoline engine may be better suited yet still provide the horsepower necessary. Review what you need to pull your fleet through.

Fuel Efficiency – Diesel fuel offers greater BTU content compared to gasoline, which contributes to the increased power to fuel-consumed ratio, aka MPG. This translates up to a 35% greater fuel efficiency compared to gasoline engines with the similar horsepower rating.

Service Longevity – How many miles does your average fleet vehicle drive per year? Essentially, you need to determine if the added cost of a diesel will pay for itself over time. If you calculate at least 25,000 miles, the diesel will make sense. Below that number a gasoline engine will be your best option. Why? By calculating your fuel/cost comparison with the life expectancy and resale costs, the payback period for the vehicle will be sooner in miles for a gasoline vehicle. Diesel pays back with additional MPG during the lifecycle.
Fuel Cost – With the advent of ULSD, the cost of refining diesel has risen significantly above gasoline and will likely remain at this level for the foreseeable future. Using ultra light crude oil from the US, which is produced from fracking, is keeping costs down because Bakken shale from North Dakota is inherently low in sulfur. The advantage may prove that diesel costs will remain steady but the reality is that we will be experiencing a glut in the compressed natural gas (CNG) market due to these conditions with fracked oil. Something for a fleet manager to consider in the next category.

Conversion – Unlike diesel engines, gasoline engines can be converted easily to run on CNG and propane with simple modifications. So popular are these conversions that mainstream manufactures are gearing their fleet production units to CNG due to the increased demand from large fleet operators. Companies like UPS, FED EX, and Budweiser have made the switch to CNG and soon many smaller fleets will do the same. Expect the availability of CNG to increase as well, already in place at many truck stops and soon to local fuel retailers to appease their fleet customers.
Maintenance Cost – maintaining a diesel engine is certainly more costly than that of a gasoline engine. Service intervals are sooner in some cases and oil reservoirs, filters, water separators, all have larger capacities and more expensive to replace. Not to mention the additional expense of maintaining a DEF system with the diesel
Intended Usage – A diesel engine is ideal if your fleet does towing or using engine driven equipment to power accessories like bucket lifts, booms, or other hydraulics. Diesels are also a good choice if you intend to have your trucks idle often between runs, like refrigerated units. That’s due to the engine’s compression ratio, which is about 17:1 for diesel versus 9:1 gasoline. This lets the diesel engine power up at a lower rpm, using the torque needed without spending more fuel. Which is why a PTO option is available for most commercial diesel engines but hard to find with their gasoline cousins.
Resale – diesel’s fare better at the time of resale for the simple equation of more competitors for that used work vehicle. There are many small companies who are in need of quality vehicles and a diesel with 150,000 miles in less than half through it’s foreseeable lifespan. Compared to the 200,000 life cycle of a gasoline engine, it’s an easy decision for the used work truck buyer.”
Environmental – Several years ago, diesels were known as the dirty polluters in our air. It wasn’t uncommon to see daily black soot pouring from smoke stacks and tailpipes, a tell tale sign of a diesel engine. Today, with less than 15 ppm of sulfur in diesel fuel and exhaust treatment technology, diesels are considered as clean as gasoline engines by the general public. Although the greenhouse gas emissions for diesel may be more per unit, the efficiency of diesel negates the emission comparison. Meaning, mile-to-mile, diesel and gasoline are just about equal in emissions produced.