Why People Are Still Converting Their Cars to Run on Propane

Although other alternative fuels like E85 get a lot of attention, LPG remains the world's third-most popular engine fuel—and it makes sense.

It’s clear at this point that more than one fuel will power the auto industry going forward. Gasoline will stay on top for who knows how long, and diesel is still the go-to option for a lot of applications, but it’s anyone’s guess beyond that. Porsche is betting on renewable e-fuels, while Toyota is convinced that hydrogen is the answer. But at present, neither of those is as widely used as propane auto gas, an oft-forgotten option that’s actually the third most popular engine fuel in the world.

This isn’t an ad for the propane industry, I promise. Instead, I want to take a second and explore why propane has so much staying power in the alternative fuels space. I remember school buses growing up that ran on propane, and I even had a science teacher whose F-150 was converted to burn liquefied petroleum gas. That said, I had no clue it was the “best of the rest” outside gas and diesel—at least, in terms of popularity.

It was brought to my attention when the people at Suburban Propane reached out about one of their employees who had performed a propane swap on his EcoBoost Ford Mustang. “That’s pretty neat, but why?” I asked myself. That’s what I set out to learn.

John Barnett is the Mustang owner in question. Professionally, he’s a National Auto Gas sales rep for Suburban Propane. Recreationally, he’s a drag racer who was looking to mix two of his passions: propane and the quarter-mile. (You thought I was going to make a King of the Hill joke, didn’t you?)

“It was important for me to showcase what propane can do beyond traditional applications,” Bartnett said. “It’s not widely known, but propane is actually a high-octane race fuel, with an octane rating between 113 and 125.”

It’s also a heckuva lot cheaper than race gas, with a gallon of LPG costing around $2.50 on average. Where I live in Missouri, it’s actually under $2 a gallon right now. Compare that with more traditional 104-octane fuel, which costs $12 per gallon—if not more, even when buying in 55-gallon barrels.

As for Barnett’s car, he’s made a handful of upgrades to accompany the propane swap, more than making up for the power difference in what he lost by swapping to LPG. An NX2 turbo is the headlining mod, along with the familiar Roush cold air intake, high-flow exhaust, and 28-by-11.5-inch tires. What’s maybe most interesting is what Barnett’s car doesn’t have, and that’s a bigger intercooler.

That’s because propane runs incredibly cold. It has a boiling point of -44 degrees Fahrenheit, which helps keep intake temperatures way down. Along with safely adding more boost, Barnett is also working with increased air density—turbocharged engines love increased air density. Just ask Gale Banks.

Then there’s the sustainability aspect, which might be less exciting for some, but it’s no less important. To understand this some more, I spoke with Doug Dagan, vice president, strategic initiatives of renewable energies at Suburban Propane. His title suggests that he’s some fancy pants executive, but early in his career, he started as a chemist.

“When you have diesel or gasoline, there are chains of carbon atoms, and they are pretty long,” Dagan explained. “The way you get energy out of them is you break the chains apart, and that releases energy, which is what’s actually happening in an engine when it combusts.”

On the other hand, propane is far simpler with just three carbon atoms and eight hydrogen atoms.

“If you have a tank of propane, the amount of other stuff in it is very small compared to a tank of diesel,” Dagan continued. “And so, when you burn it, you get a lot less particulate matter than you do when you burn diesel or gasoline. So, that’s sort of the fundamental reason why it’s cleaner for air quality. For climate quality, the reason it’s cleaner is that it puts out a higher amount of energy per break and per carbon molecule that gets emitted than diesel or gasoline. So, it’s a cleaner molecule from a climate perspective, too.”

Finally, there’s the production aspect. See, propane is a byproduct of crude oil refining and natural gas processing. Because it’s captured during those events, no one is going out to dig or drill for propane.

Not everything about propane is an improvement over gasoline. There’s the aforementioned slight power drop, as a gallon of LPG also has 27% less energy than a gallon of gasoline. That means it also returns lower fuel mileage. (To address that, Barnett’s personal truck actually starts on regular gasoline and then switches to propane auto gas. This dual-tank setup enables him to drive around 750 miles between fill-ups.) LPG also doesn’t have the same lubricating properties as its more conventional counterparts.

I don’t expect to see a mass exodus of gearheads from gasoline to propane in my lifetime. That said, it clearly makes sense for some folks depending on their use case and ease of access to LPG stations. It might not be the designated fuel of the future for Porsche, Toyota, or whoever else, but it’s chugging along steadily at third in the world behind gas and diesel for a reason.

By Caleb Jacobs