Diesel (compression) engines have been around since 1892, making them nearly as old as gas (combustion) engines, which date to around 1860. The two fuel choices have always been very different and over the years, at least in the U.S., each has come to dominate its own vehicle segment—diesel in trucks and gasoline in cars.

But now, in large part due to diesel emissions regulations increasing the costs and complexity of those engines, gas is becoming the preferred fuel choice for some, even when it comes to trucks.

Bob Stanton, a former fleet manager and now fleet management consultant based in Georgia, has been arguing for years that diesel makes more sense than gas when it comes to smaller (Class 3-6) fleet trucks. For starters, he says that while diesel cars enjoy a significant miles-per-gallon advantage over gas equivalents, there’s not as much of a difference in fuel efficiency when it comes to trucks.

While gas is gaining popularity in smaller trucks, larger trucks are still dominated by diesel. “When you have a full load of chips and a chipper being towed behind it, that’s one place where a diesel really pays off,” says Peter Jeskey, vice president of capital equipment for Bartlett Tree Experts.

PHOTO: BARTLETT TREE EXPERTS

“And the mpg gap is growing ever smaller,” Stanton says. “In my experience, it’s typically 1 mpg or less.”

At the same time that the fuel economy of gas engines is increasing, so too is the power. “The cool thing about gas is how much power it offers in the lower speed ranges,” Stanton says. He cites, as an example, small transit buses (F-450 and F-550 chassis) he purchased when working as a fleet manager. “When we switched to gasoline the drivers were actually very happy due both to the low-end pick up and less noise,” he says.

Especially in the category of pickups, gas engines are gaining popularity among the tree industry fleet managers we spoke to.

“We’ve moved toward gas engines in our pickup trucks. In the last year, I’ve mostly phased out the diesel pickup trucks,” says Roger Scott, fleet manager with Kramer Tree Specialists in Illinois.

He notes that the company’s larger trucks are still diesel, but says that, at least with pickups, there have been many advantages in moving to gas. “There were just too many costs associated with diesel… when they start getting 80,000 or 90,000 miles on them, you get a lot of issues, and very expensive repairs.”

And the upfront costs are much lower, as well, he says. “I’d say it’s anywhere from a $10,000 to $15,000 upgrade from a gas truck to a diesel truck,” Scott says. He says the drop in gas prices has made the equation even better, but it’s the lower maintenance requirements of gas engines that make the biggest difference. “Really, the only services we have to do to them is to tune them up at 100,000 miles, and that’s really just a set of spark plugs,” he says. There’s also no need to plug in the gas-powered trucks in the winter, Scott adds.

“Ninety-nine percent of our pickups are gas-powered,” reports Peter Jeskey, vice president of capital equipment for Bartlett Tree Experts. “We have a few diesels, but those are in offices that are specifically doing a lot of towing, like towing heavy chippers.”

Unless the diesel is truly needed, Jeskey opts for gas pickup trucks in large part because the initial cost is much lower. And, at least when it comes to pickups, he isn’t as concerned with the longer engine life that a diesel could offer. “By the time the pickup has a couple hundred thousand miles on it and is just about worn out, the gas engine is probably in the same situation. A diesel engine might have half a life still ahead of it, but who cares if everything else is worn out,” Jeskey states.

Bigger rigs

Jeskey says that Bartlett’s production fleet of larger trucks remains nearly all diesel. In these applications, longevity is a bigger factor for him. “A diesel engine is going to last longer than a gas engine,” he states.

Not that he hasn’t experimented with gas power in larger trucks. “With the advent of Tier-3 and Tier-4 emissions, a lot of people are looking at gas alternatives. And we are one of them,” Jeskey says. The company recently tried out some gas- powered Ford trucks (19,500 GVW). “We found them to be very, very thirsty,” he notes of the fuel efficiency.

Power was another area of concern: “When you have a full load of chips and a chipper being towed behind it, that’s one place where a diesel really pays off. The crews are so used to diesel. Everything has been diesel forever.” He said the crews seemed to miss some of the power and torque of diesel, especially when working in hilly areas.

Kramer Tree Specialists has mostly switched its pickup fleet from diesel to gas models, such as the model seen here. The upfront costs are lower, and so are maintenance expenses, reports fleet manager Roger Scott. “I have yet to hear a complaint that they won’t tow anything that we have,” he adds.

PHOTO: KRAMER TREE SPECIALISTS

As much as performance, it may be a lack of options that keeps more fleets from introducing larger gas-powered trucks. “Availability is an issue,” when it comes to gas engines in larger commercial trucks, Jeskey says. “Dodge goes up to 19,500. Ford is the only manufacturer currently offering a gas engine in anything over 19,500 (GVW). My concern with that is that it doesn’t have an air brake option, and that’s something I look for whenever I can get it.”

While diesel engines still dominate in the larger trucks, they are not the same diesel engines from years past. For example, one traditional reason for choosing diesel was in applications when significant idling was required. But that’s changed, Stanton says.

“In today’s world with selective catalytic reduction (SCR) emission systems since 2010, idling will do more harm than good to a diesel engine,” he explains. “For SCR to work properly, the engine temp must be high for extended periods of time to keep the diesel particulate filter clean. Extended idling in a bucket truck application, for instance, keeps the engine temp below optimum for extended periods causing the diesel particulate filter (DPF) to accumulate unburned exhaust particles causing it to fail prematurely. Cleaning or replacing a DPF is expensive.”

The emissions regulations have led to a lot of extra maintenance on diesel trucks of all sizes, agrees Kramer Tree Specialists’ Scott. And it’s one of the main reasons he’s moved away from diesel pickups.

“Especially with the EGR (exhaust gas recirculation) coolers; we’ve had a lot of problems with those systems plugging. And if you have a truck that has to idle a lot, the EGR systems really don’t like that,” he explains. “Before reaching 100,000 miles, we were running into problems that were unavoidable, and easily cost $6,000 or $7,000.”

“Tier-3 emissions were tough on the truck manufacturers [to design], and tough on the drivers [to operate],” states Bartlett’s Jeskey. “All of a sudden, there was a regeneration button. Nobody understood what it meant and how to properly do a regeneration. And manufacturers really didn’t either, because Tier 3 got pushed on them pretty quickly.”

Tier 4 wasn’t as bad as far as adding complexity out in the field, because manufacturers had added refinements and drivers had gotten used to the new technology. “Tier 4 has been out for six years now, and we have very few issues with that now,” Jeskey says.

He notes, though, that Tier 4 now includes equipment like chippers, and there is concern that this will again add complexity. “If you’re doing a regeneration in a truck, the truck has to be at normal operating temperature and anything you do, like touching the brake, is going to throw that regeneration process off. But chippers sometimes only run four or five minutes at a time, so will they get to normal operating temperatures? There’s just a lot of things we don’t know.”

With this uncertainty, Jeskey is currently testing out a 15-inch gasoline-powered chipper. “It’s been getting some very good reviews,” he says of the reports from the field. There’s about a $7,000 lower initial cost for that machine versus a comparable diesel chipper, he notes, adding that, “We don’t know yet whether we’re going to get the same life out of it.” He’s also concerned that, out in the field, someone is going to eventually fill the gas tank with diesel fuel. Like with trucks, he expects larger chippers to remain diesel-powered, while there will be more gas options in smaller chippers.

FROM A MANUFACTURER’S POINT OF VIEW

We wanted the perspective of an equipment manufacturer regarding the debate of gasoline versus diesel. We spoke with Bob Dray, vice president of sales and marketing (forestry division) for Utility 1 Source, which is comprised of five family-owned and operated businesses: Custom Truck & Equipment, Utility Fleet Sales, Forestry Equipment of Virginia (FEVA), UCO Equipment and TNT Equipment.

Here’s what he had to say:

“We’ve had several of our customers comment on their choice regarding gas or diesel engines in their fleet. The main focus will most likely be on cost of fuel. If diesel stays where it is, the push to move to gas will be less, but if the price of diesel escalates, the trend toward gas will rapidly strengthen. One other thought will be the cost of the gas chassis versus the diesel—if that separation is significant and the cost of ownership favors gas, we’ll see a strong push toward the gas chassis. This will, of course, be predicated on the availability of gas class-7 chassis.

There are some other reasons where gas has benefits. For example, colder temperatures will favor gas as it doesn’t have gelling issues. Now that Tier-4 gas engines have become prominent in the chipper business, many customers don’t want to have to fill up with two different fuels, so that leads them toward a gas unit.

Finally, many states following the Clean Air Act are moving away from diesel fuel, which in the long run will perpetuate the use of cleaner burning fuels.”

Convincing crews

Diesel has gained a reputation over the years for offering superior power and torque, which may make crews resistant to switching to gas-powered trucks. Stanton says that one of his goals is to help provide fleet managers with adequate justification to dispel the notion that diesels are “better” than gasoline engines in light- and medium-duty trucks. He says they can help to lay out the facts about the engines, and also what goes into selecting which to buy. “As fleet managers, we’re charged with making the best financial and operational decisions to keep our companies, departments, etc., in the black,” Stanton says. “Opting to save money by investing in equipment wisely preserves jobs and makes salary adjustments more available without compromising operational effectiveness. End of story.”

“I know why everybody went to diesels in the past, but now the gas engines get fuel mileage that’s just as good, you get the same power output, and gasoline now costs less than diesel,” Scott says. He says that the gas pickups Kramer Tree Specialists is operating now run the gamut from lighter-duty models up to larger 1-tons. “We have some Fords with the 6.2L gas engines in them, and I have yet to hear a complaint that they won’t tow anything that we have,” he says.

Scott adds that gas trucks offer one advantage over diesels that should appeal to those working in the field: “When you’re in a neighborhood, they don’t sound like a coffee can full of nuts and bolts pulling into the driveway.” In fact, he recently added a gasoline-powered skid-steer to the fleet in part for the same reason, that it’s quieter to operate in residential areas.

At Bartlett, Jeskey has found an even quieter option, at least when power and torque aren’t considerations: “At least one-third of our sales vehicles are hybrids, mainly the Toyota Prius.” Many of those who operate this part of the fleet love them, and for the ones that don’t, “it’s purely for the image—they want to be a macho guy and drive an SUV!” Jeskey jokes. “I do have to say that the Prius has been the most reliable and has had the best return on investment of any sales car that I’ve ever bought. The cost-per-mile is small but the resale value is tremendous.”

Who knows, if electric technology continues to develop, it may be that, in the future, trucks aren’t fueled by fuel at all.

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