LP-Powered 2008 Roush Ford F150

I get in, turn the key, and suddenly I’m inexplicably dying to have a barbeque. It’s a feeling I can’t shake because I’m driving an otherwise stock 2008 Ford F-150 that’s powered by liquid propane (LP), that ubiquitous grill fuel. (Methinks the column shifter should be a spatula.)

Our subject F-150 features fuel-system modifications developed by Roush Industries, the same folks who build all manner of high-performance Mustangs and contributed engineering expertise to the Ford GT supercar. This particular truck is designed for fleets that have easy access to propane, thus nullifying concerns over having to daisy chain a series of Rhino tanks. Although the current customer demographic includes municipal and commercial fleets, the push to run vehicles on something other than gasoline is likely to entice private citizens to consider propane in the coming years.

The Roush Conversion
Roush’s offering is serious, as it matches the significant capabilities of the gasoline-fired F-series when it comes to crankshaft horsepower as well as payload and towing. Roush currently offers LP conversions for just about any 2008 F-150 powered by the 5.4-liter Triton V-8 engine, which is available in trucks offering three cab choices, three bed lengths, and five trim levels.

The conversion’s focus is the fuel system. Changes begin with storage; Roush offers two fuel tank sizes, a 25-gallon bagel-shaped Toroidal holding cell that occupies the same location as the truck’s discarded gasoline tank and a larger 59-gallon drum-type unit that fits in the bed. According to Roush, most customers go for the larger tank because of its 500-plus-mile range and simply deal with the reduced bed volume.

Forward of the tank, Roush replaces everything fuel-related, including custom billet fuel rails that carry liquid propane to custom injectors. Given LP’s natural tendency to vaporize when not under pressure, the fuel atomizes as it exits the injector, creating an easy-to-combust charge.

To take advantage of propane’s higher octane equivalency (99 to 112 octane R/M, depending on the refiner), Roush engineers reprogrammed the F-150’s engine control module. The resulting output matches the gasoline-powered F-150’s 300 hp and 365 lb-ft of torque. Given this consistency, it’s no surprise that everything inside the engine remains stock and fully covered under Ford’s factory warranty. Roush backs its hardware separately.

Driving With Propane
From inside the Roush-modified F-150, there’s nothing to tip you off that you’re driving a propane-powered truck. It drives like its gas-burning counterpart in almost every respect, except how it starts. When you key the ignition, the gauges come to life and the radio turns on, but nothing else happens. If it’s cold out, the fuel system takes up to ten seconds to pressurize. Then, once it’s darn good and ready, the starter motor magically engages and the truck fires. (On warmer days, or when the engine is at operating temperature, the starting sequence requires less than three seconds.)

The truck quickly settles into an idle that’s just as smooth as that of the standard 5.4-liter Ford V-8. It sounds the same, too. Importantly, the powerplant doesn’t exhibit any cold-blooded characteristics, and the truck can be driven away from the curb as quickly as the driver moves the shifter into D.

On the road, my initial concerns about carrying 59 gallons of fuel above the axles are quickly allayed. The Super Crew Cab is designed to haul more than 1700 pounds of payload; LP weighs 4.23 pounds/gallon, so a full tank weighs less than 250 pounds. The truck’s handling and braking capabilities aren’t stressed by the new fuel system, and we confirmed this during a week of driving.

Spending so much time behind the wheel gave us the chance to evaluate Roush’s revised programming for the engine control module. Often, modified vehicles have advantages in some dynamic tests but suffer in normal driving situations. Not so with the Roush truck. Very gentle throttle applications generated very smooth acceleration. Jumping on the right pedal launched the truck with authority, and there were no flat spots in the acceleration. In a word, Roush’s new powertrain calibrations are perfect.

Since Roush changed nothing else in the truck, our rear-wheel-drive XLT Super Crew performed exactly like a gasoline-powered 2008 F-150 in all other respects, including ride quality and quietness. In light of the recent launches of the 2009 Dodge Ram and the 2009 F-150, however, it’s clear that the 2008 F-150 is getting old in terms of handling dynamics and ride refinement. At this time, Roush hasn’t announced a conversion for 2009 F-150s.

Regarding fuel economy, the F-150 travels about 10 percent fewer miles per gallon on LP than on gasoline, so average driving delivers about 13 mpg. This loss is more than made up for by the lower cost of LP fuel, which usually tracks about 75 percent of the cost of gasoline. The net is that an LP F-150 costs less to run per mile than its gasoline-swilling counterpart.

Facts about LP – A cleaner fuel that’s not just for grills
According to the U.S. Census circa 2000, almost seven million American households use propane as their primary fuel. The Department of Energy estimates that there are 250,000 vehicles on American roads powered by the fuel and close to a million worldwide (the fuel was particularly popular in Australia through the 1970s and ’80s). Curiously, the fuel is a byproduct of refining gasoline and natural gas. Among LP’s many benefits, it converts easily to liquid under light pressure, making it easy to store and transport. Propane refills take about the same time as a stop at a gas station, as the liquids flow at about the same rate. Additionally, propane vaporizes at normal atmospheric conditions, so fuel spills are literally impossible (the fuel immediately evaporates).

Chemical analyses reveal that LP is a cleaner fuel than gasoline. When burned, propane emits 40 percent less particulate matter, half the NOx, and 87 percent fewer hydrocarbons. Proponents also purport that engines run cleaner on propane and require less maintenance because the fuel leaves fewer contaminates on cylinder walls and in crankcase oil. Roush makes no such claims, but the company doesn’t dismiss the notion, either.

As for refueling, sources at Roush recommend checking out Coverage in metro markets is strong, and with a little planning, a cross-country trip in an LP-powered vehicle isn’t out of the question. When refueling, it’s important to note that there are three different types of LP: propane, engine fuel-grade propane (known as HD5), and commercial-grade butane. HD5 is the only engine fuel-grade propane.

Too Rare or Ready For Consumption
Roush’s Liquid Propane F-150 conversion certainly performs like a “real” truck and presents drivers with few compromises compared with a traditional gasoline F-150. The high cost of the conversion (an all-inclusive retrofit costs $9,300 for a torodial tank system and $11,300 for the in-bed tank system) is daunting to an average consumer, but significant federal tax credits and the lower cost of LP (compared with gasoline) mean that the added cost likely would be saved after several years of ownership.

LP-fueled automobiles won’t free America from its dependence on foreign-sourced oil, but it does demonstrate that alternative fuels can provide the same level of performance from a familiar platform while delivering a greater level of efficiency.

This, my friends, is progress. Let’s enjoy a grilled bratwurst to celebrate…

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Buying Guide
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2008 Ford F-150

2008 Ford F-150

MSRP $26,480 STX 4WD Styleside Regular Cab


14 City / 20 Hwy

Payload (Max):

1,800 lbs.

Horse Power:

202 @ 4350