Slick roads, poor visibility, freezing temperatures, and traffic delays are among the challenges fleets may face each year as colder temperatures arrive. However, the wheels don’t roll if the colder temperatures negatively impact fuel systems.

What fuel choices are most impacted by cold weather, which have the least concerns, and where do battery-electric vehicles fall within that continuum?

Diesel Care: Prevent Gelling

Eric Simms, a product development and quality control manager at Rislone, said the biggest problem associated with diesel fuel in cold weather is fuel gelling.

“There's paraffin wax in diesel. It's just part of the process at the refineries. It's in all diesel, no matter what,” Simms explained. “And in those cold temperatures, it can cause it to gel or kind of thicken up.”

That, he continued, can cause clogging and problems in fuel filters and fuel lines, and result in engines failing to start or starting to stall.

“Gelling can cause downtime. Repairs and maintenance are one thing, but downtime is also costly,” he pointed out.

While there is no official temperature at which gelling begins, temperatures do not have to reach freezing. Simms said as temperatures drop to around 40 degrees, it’s time to keep gelling in mind and prepare.

“It doesn't have to be technically freezing, but just being cold can cause gelling to start. But definitely, once you get down to below freezing or even closer to zero, every degree that it drops, it definitely will exponentially gel up more and more,” Simms explained.

Gelling may first start where the diesel fuel is found in a smaller volume, like fuel lines, with the fuel tank, a larger volume, gelling later.

When gelling occurs, results can vary. Possibly, a diesel engine may fail to start. Or, it may start but then have to be idled for a while, which increases fuel consumption. But, gelling can also cause stalling.

“If you're able to get it started, and it essentially sucks up a big hunk of that paraffin wax that's gelled in there, it can cause it to stall out and then leave you on the side of the road,” Simms cautioned.

But, fleets can prepare for the fight against fuel gelling.

First, Simms said it is important to use winterized diesel when available. That availability is seasonal, likely becoming available at the pump in the colder areas first.

Next, even with winterized diesel, Simms said it is important to use a fuel additive with anti-gelling properties. That is even more important in warmer environments found in the southern states, where winterized diesel may not be readily available at the pump as easily as in places like Michigan, Minnesota, or other seasonally colder areas.

Additives, like those from Rislone, can be used at any time, and there is no need to wait for the bitter cold. Simms pointed out that typically, the additive will need to go into the tank about every 5,000 miles.

But, does it matter when you pour in the additive? Should it be on an empty tank, or another approach?

“I personally typically recommend maybe a half-full tank, just so that you're getting a little bit stronger dosage, getting into the system, and then topping up,” he suggested.

Diesel-powered fleets also have to be prepared for cold starts and a loss of efficiency in cold weather when the lower temperatures can thicken the oil and reduce fuel volatility. According to Simms, all of that can result in a decline in fuel efficiency.

“We recommend, obviously, if you can keep it inside in a warmed building, that would be ideal. But engine block heaters can help to keep those issues from happening,” he explained.

For fleets that operate both diesel and gasoline vehicles, while diesel may require more care and preparation during the colder seasons, gasoline does not pose the gelling concerns.

Condensation Concerns

Whether running on diesel or gasoline, fleets need to keep fuel tanks filled to reduce condensation and water buildup in the fuel.

Condensation formed in a partially filled tank promotes the growth of microorganisms that can clog fuel filters and restrict fuel flow, pointed out Brian Kernke, general manager of fuel quality for Love's Travel Stops.

Fuel filters and heaters should be checked, and Kernke suggested draining the water weekly out of the fuel filter using the filter drain valve.  He also recommends draining off any water and/or sediment by opening the drain at the bottom of the fuel tanks. 

Propane Autogas: Ready to Roll

So, for fleets powered by propane autogas, what are the winter fuel concerns?

Actually, there are none.

“Propane autogas really doesn't have any concerns or issues with cold weather. It's more of a misconception that people have about propane,” said Joel Stutheit, senior manager of autogas business development at the Propane Education & Research Council (PERC). “Propane doesn’t change from a vapor to a liquid state and become unusable in engines until negative 44 degrees Fahrenheit, so the cold weather doesn't affect it or the performance.”

Stutheit pointed out a key advantage of propane autogas is that there is no need for engine block heaters and no concerns about fuel gelling, as there are with diesel. But, that does not mean to turn a blind eye to regular maintenance on propane autogas vehicles just because it’s winter.

“Just like any other systems, you're going to do your routine inspections to make sure that you're up on the maintenance of it and everything is in good repair,” Stutheit added.

And Stutheit pointed out another advantage of propane autogas over diesel, and that is tied to efficiency.

“One thing about propane auto gas vehicles is they actually warm quicker than diesel vehicles, so you don't have that long lead time of idling in cold weather,” he pointed out. “Drivers are able to start that vehicle and get it on the road quicker than with a diesel.”

Battery-Electric Fleets

Battery-electric vehicles face several challenges in cold weather, but fleets can take steps to mitigate some of those.

Scott Zion, chief product and engineering officer for Motiv Electric Trucks, has worked with battery-electric vehicle platforms for more than 30 years.

According to Zion, the main challenges for BEVs in cold weather are reduced range, longer charging times, increased energy demand for heating, thermal management inefficiencies, and reduced regen in slippery conditions.

Cold temperatures slow down chemical reactions in lithium-ion batteries, which can reduce available driving range by 20–40% or more, depending on conditions and vehicle configuration, Zion said.

But with the cold also comes charging challenges.

Battery packs charge more slowly when cold, and in some extremely cold conditions, they won’t charge at all until the pack is heated to a suitable level first. Zion said even DC fast charging can be significantly impacted if the battery isn't pre-conditioned or pre-heated.

However, to confront those two key challenges and the others Zion shared, fleets can take steps to prepare for winter.

Zion suggests fleets ensure trucks and chargers support battery and cabin pre-conditioning — heating the battery and cabin before departure or before charging.

He also recommends installing or enabling heated enclosures or shelters around chargers to reduce the impact of ambient cold, especially in regions with subzero temperatures.

Also, ensure battery management systems (BMS) and vehicle software are up to date. Winter optimizations may be included in over-the-air (OTA) updates from OEMs.

Fleets should train operators on cold-weather driving best practices, like limiting HVAC use and planning for extra charging time. It is also important to make them aware of how the weather can impact regenerative braking.

Cold-weather maintenance checks are also important. Inspect and maintain insulation, thermal management components, tires, and brake systems since regenerative braking may behave differently in cold weather.