It wasn’t all that long ago most vacuum excavators on the market were equipped with a diesel engine. Units with a gas engine were thought to be underpowered, with a shorter life expectancy than similarly sized diesel-powered units. However, today’s advanced gas engines and the added costs associated with new Tier 4 diesel engines have left many contractors reevaluating their stance on gas-powered vacuum excavators, and you should be, too.

According to Brian Showley, director of sales for Vermeer MV Solutions, the capabilities of gas-powered vacuum excavators have expanded dramatically in the last few years. “Gas-powered vacuum excavators have always been a good option for contractors using them to support a horizontal directional drilling crew with fluid management,” he explains. “However, many older gas models couldn’t move enough cubic feet per minute of air to efficiently pothole buried utilities. Today, there are high cfm gas-powered vacuum excavators available that are more on par with similar-sized diesel units.”

Market shift

More than two decades ago, the U.S. Environmental Protection Agency introduced a tiered series of emissions regulations designed to reduce the carbon footprint of off-highway equipment. Since going into effect, engine and equipment manufacturers have worked together to meet each of the EPA’s tiered regulations, and today’s advanced Tier 4 diesel engines are the results of that work. Tier 4 final engines reduce carbon emissions, increase fuel efficiency, and allow for longer service intervals, but cost significantly more to purchase. 

Meanwhile, as diesel engines were being reengineered to be compliant with Tier 4 regulations, smaller gas engines were also being redesigned with sophisticated computer controls and high-pressure fuel delivery systems to optimize power and fuel efficiency. Today, most gas-powered vacuum excavators have electronic fuel injection engines that are much more reliable and powerful than older carburetor engines.

“The rising costs of purchasing diesel-powered equipment and the performance improvements of EFI gas-powered machines is leading many contractors to run more of a mixed fleet,” Showley says. “The switch started with the trucks they drive to the job and is expanding to support equipment including vacuum excavators. It’s a trend that is likely to continue as long as they don’t have to sacrifice performance. In fact, contractors working in colder climates might be better off with an EFI motor because they start much easier on cold days.”

High cfm

Gas-powered vacuum excavators have been around for many years, but Showley says he has noticed a shift in use since Vermeer MV Solutions introduced its Vac-Tron CV SGT high cfm vacs with a 1,000 cfm vacuum pump powered by a 38 hp EFI gas engine. “Contractors used to complain that gas engine vacs didn’t have enough suction power for potholing in clay and other challenging soil conditions,” he explains. “The introduction of high cfm gas models changed that. These new models deliver the same vacuum performance and have the water pump capacity to deliver plenty of pressure to loosen up material. There is not much of a performance difference between high cfm gas vacs and diesel-powered units in the 3- to 4-inch-diameter hose size vacuum excavator market anymore.” 

The similar performance levels of high cfm gas-powered vacuum excavators also have a lower price tag than their diesel counterparts. “While gas-powered vacs are more economical to operate because of the lower upfront purchase price, gas engines tend to not last as long as a quality diesel engine,” he says. “That is the trade-off that contractors need to wrestle with. However, in many instances, the price difference between gas and diesel engines is substantial enough to offset the costs of having to replace a gas engine down the road. Over the road, gas-powered vacs have an advantage because they usually don’t weigh as much as diesel units. A difference of a few hundred pounds can make a big difference when hauling a full tank of slurry.”

Choosing diesel

Investing in a quality vacuum excavator with a diesel engine is still a solid investment for contractors. The fact of the matter is, diesel models will likely hold their value better than gas-powered units, which makes a difference for any contractor who likes to upgrade their fleet often. Also, while gas-powered vacuum excavators match up pretty well within the 3- to 4-inch hose size class, diesel is still king in the larger vacuum excavator sizes. “Maybe someday gas engines will be able to better compete in those higher categories, but for now advances in the smaller categories are leading the way.”

Gas or diesel vacuum excavators — the choice is up to you. If you need help weighing your options, be sure to contact your local Vermeer dealer or visit vermeermvs.com.