Gas Vs. Diesel F-550 Bus: The Pros & Cons of Each Engine Type

One of the most common questions operators ask us when considering an F-550 shuttle bus is whether they should get a diesel or gasoline engine. It’s an important question to ask because they have different characteristics that can affect the bus’s performance and operational costs. To make the things easier, we’ve identified several factors that every operator should consider when debating between a diesel or gasoline engine for their F-550 bus.

Horsepower  / Torque

The first thing to understand about gasoline and diesel engines is that there’s a trade-off between horsepower and torque. Gas engines are designed to rev faster, meaning they generally produce more horsepower than diesel engines, but don’t have as much towing capacity or pulling power. A diesel engine, on the other hand, may have slightly less horsepower than a gas engine, but much greater torque, making them a better choice for powering heavy buses, especially in geographic areas with steep grades and hills.

Deanna Sclar’s helpful analogy  puts the two engine types in perspective: A gasoline-powered engine is like a racehorse -- high-strung, fiery, and fast -- whereas a diesel engine is more like a workhorse -- slower, stronger, and more enduring.

With that said, it’s important to consider the terrain on which you’ll be operating your bus. On relatively flat roads, Ford’s 6.8-liter Triton V-10 gas engine, rated at 362 horsepower and 457 lb-ft. of torque, will do just fine. But if you run your shuttle bus up and down steep hills, the gas engine may feel a little underpowered, especially with a full load of passengers and their luggage. In that case, we recommend equipping it with the 6.7-liter Power Stroke V-8 turbo diesel engine, which is rated at just 300 horsepower but with a whopping 660 lb-ft. of torque. Chauffeurs and passengers alike will benefit from the diesel’s ability to conquer hills and slopes with ease.

Fuel Economy

One of the major benefits of a diesel engine vs. a gas engine is the better fuel economy it provides. Because gasoline has a lower energy density than diesel, it takes more gas to equal the power output of diesel. A diesel engine is thus more efficient per gallon of fuel burned. Diesel engines also use only about ⅓ as much fuel as gas engines do during idling.

This gives diesel engines the ability to produce significant cost savings over the lifespan of your bus.

Maintenance

The difference in maintenance requirements between a diesel and gasoline engine can be split into short term and long term.

In the short term, diesel engines typically have higher repair and maintenance costs than a gas engine because they require specialized technicians and have more complex parts that need to be maintained.

However, in the long term, it can be more cost-effective to own a diesel engine because of its durability; fewer overall repairs will be required compared to a gasoline engine. A diesel engine has a longer lifespan than that of a gasoline engine, which allows operators to run diesel-powered buses longer than gasoline-powered buses as well as benefit from a higher resale value.

Price Point & Cost of Ownership

It's important to note that the initial purchase price of a vehicle and its total cost of ownership are two different things. While purchase price plays a big role in determining a vehicle’s true cost of ownership, it’s not the only piece to the puzzle.

While it would be ideal to pay a set price to own and operate a vehicle for its lifespan, we all know that's not realistic. Vehicles require fuel, maintenance, repairs, and sometimes upgrades, all of which add costs beyond the purchase price and affect a vehicle’s profit margins.

A bus with a gasoline engine has a lower purchase price than a bus with a diesel engine, and depending on the cost of fuel, may be more affordable to operate. However, a diesel engine may be more durable over the bus’s lifetime, meaning fewer repairs and less downtime; combined with better overall fuel efficiency, a shuttle bus powered by diesel may end up having the same or lower cost of ownership as a bus with a gasoline engine.

Bonus: One More Advantage of a Diesel Engine vs. a Gasoline Engine

According to Steve Ciatti, a mechanical engineer at Argonne National Laboratory, diesel engines perform better at higher altitudes than gas engines. The air is thinner at high altitudes (there are literally fewer molecules of air per cubic foot), and gasoline engines operate at a very specific ratio of fuel and air. At higher altitudes, gas engines have to add less fuel to keep the fuel-to-air ration perfect, and this affects performance.

Diesel engines, on the other hand, run “fuel-lean, so you don’t have to keep the ratio perfect,” Ciatti says. They have pumps driven by exhaust gas called turbochargers, which add more air to the combustion chamber; more air means more fuel can be added, so at high altitudes, they pull in more air to allow more fuel to be added, which provides more power than a gasoline engine.

Bottom Line

With all of this information, you may still be wondering which bus engine to get on your Grech F-550 bus. Based on our findings, you will benefit from a diesel engine if:

  • You operate at higher altitudes

  • You will have longer-distance trips

  • Your fleet cycle is greater than 5 years

  • You operate in regions that have steep grades going uphill

You will benefit more from a gasoline engine if:

  • You don’t have access to qualified diesel engine techs

  • You operate in relatively flat areas

  • The initial price point and lower cost of gas in your market make a significant difference to your company’s bottom line

Ask Other Operators

At the end of the day, there are a lot of factors to consider, but the decision may come down to something as simple as availability of gasoline or diesel in your area. If you aren't sure which route to go, you can always reach out to other operators to get their feedback. There's a great Facebook group that serves as an open forum for limo operators to ask questions and share insights, which you can find by clicking here.

Grech Motors is a high-end coachbuilder founded by Ed Grech, who currently serves as President and CEO.