CNG Test Drive: Ford F-250 SD Bi-Fuel


GM and Ram drew quite a bit of attention at the 2012 NTEA show by announcing bi-fuel compressed-natural-gas heavy-duty trucks sold through their fleet and commercial networks. For comparison’s sake, we note that the Chevy Silverado 2500 HD can be ordered through any dealer, but it does need to be shipped to Impco for the alternative-fuel retrofit.

The Ram HD 2500 will be built on the production line in Mexico. So technically, it will be the first of the major players to offer a factory-installed bi-fuel CNG option.  However, many don’t know that Ford’s bifuel CNG program has been in place for several years, and its supplier, Westport Inc., is just feet away from the Kentucky plant production line that makes the Super Duty.

In addition to the fact these types of bi-fuel strategies will comfortably extend the range between fill-ups by, in some cases, hundreds of miles, there is the issue that CNG typically costs less than half of the cost of gasoline for a gallon-equivalent amount of fuel. (CNG, as the name suggests, is a gas.) Also, with our increased desire to become more oil independent, it makes sense that options like compressed and liquid natural gas (both of which we have huge supplies of within our borders), as well as propane (or Autogas) are going to become more and more popular.

Obviously, a changeover to or inclusion of something with a weaker infrastructure will take time to create. Even in a huge metropolitan area like Los Angeles, there are only about four-dozen filling stations available to general consumers. Thankfully, there are websites that let you know where the closest one is, as well how much fuel costs. We did all our research at    

Time for a Test Drive

With all the attention on these new vehicles and the discussion about CNG or LPG or Autogas being our best hope for a smooth and cost-effective transition away from excessive fossil-fuel use, we thought we’d get a hold of one of the most popular players in the segment and see how it performs in some real-world driving and commuting.

Our test vehicle was  with a Wesport Wing Power Systems bi-fuel conversion. Just in case anyone might not be able to distinguish the huge 18-gallon (gasoline equivalent) tank in the bed, which takes up about 30 percent of the bed space, Ford decided to put stickers all over the vehicle to make sure no one could possibly miss the fact this is a bi-fuel truck with a range of up to 650 miles. Thankfully, we had it over the Memorial Day weekend, so most people just assumed we were headed to or coming from some parade, entered as a float.

How It Works

Here’s how the Westport system works: A previously identified and box-checked Super Duty is scheduled for the CNG bi-fuel install. Westport, as a top-tier supplier for Ford, is allowed to have an on-site facility to make all the non-Ford mods and changes. For all practical purposes, this is a factory install.

The Westport system () comes with a three-year/36,000-mile warranty for the tank, fuel filler, CNG lines and gauge, and it offers a five-year/50,000-mile warranty on the fuel control module and pressure regulator, as well as the CNG fuel injectors and wiring harness. All of the Ford warranties apply to the rest of the vehicle.

The bi-fuel system costs $9,750 for the basic system with an 18.5-gallon tank and $10,950 for the larger 24-gallon setup.

A bi-fuel system, obviously, provides two sources of energy to rely on. The fuel system is biased to CNG, meaning that it will always start and run on CNG as long it is in the tank. When CNG runs empty, the system transparently switches over to gasoline. The CNG gauge sits to the right of the air-conditioning controls and looks completely factory. Blue indicator lights let you know how much CNG is in the tank, and you will not see your gasoline gauge move until it begins to flash just before it is empty.

We drove almost 150 miles on three-quarters of a tank of CNG, watching the F-250 calculate our average mpg up, up and up. We should note, assuming you reset the computer after a CNG fill-up, your Ford computer readout will not calculate your fuel economy higher than 99.9 mpg. We have to say it is interesting to drive a good distance without seeing any movement from the gas gauge, but there are some noticeable differences when driving in CNG mode.

What’s the Difference?

There is a noticeable decrease in throttle response and an overall feeling that you have a little less power at your disposal. The launch of the truck from a dead stop feels like you are carrying more load than you know is on or in the truck. Still, the 6.2-liter V-8 feels capable and sufficient to move you around town empty without any problems, but we’d be cautious if pulling or hauling heavier loads.

As our CNG ran out, we strained to observe the exact moment the truck switched over to gas, and we could not. We did happen to be on the highway, and according to the trip computer, which calculates exactly how much gasoline we use, we could see the exact moment when the computers detected the switch to gasoline, but we felt nothing. We can say that driving the truck around town on gasoline on many of the same streets we’d driven under CNG power, we could notice a slight jump in performance feel and response. But to test our butt dyno, we decided to take the truck to a real dyno shop and see exactly what the power differences were. Thankfully, our friends at K&N Engineering were able to squeeze us in on their DynoJet, and we found exactly what we’d predicted.

On the Dyno

Because the Westport system prioritizes CNG, we ran the tank completely empty, running on gasoline. We dynoed the truck on gas as a baseline run, then immediately ran to our nearest public CNG filling station (which happened to be just three miles away) and filled up the 18.4-gallon tank. The station noted that it would only fill to the 3,000-psi mark, which turned out to be 14 gallons when the pump shut off, reading our tank as full. Our tank, on the other hand, was rated to read full at 3,600 psi.  Our CNG fuel gauge inside the truck clearly read three-quarters full and at $1.83 per gallon, we spent just over $25 to “fill” the tank. We assume this filling station had a lower maximum pressure for some kind of safety or local fleet-specific reason, though it does seem odd this isn’t all standardized yet.

After our CNG fill-up experience, we headed back to K&N and ran the Super Duty on the dyno again, this time running on CNG. The comparison numbers, as suspected, were interesting and not surprising. Maximum horsepower on gasoline with our 6.2-liter V-8 was 302 at 5,750 rpm, while max horsepower on CNG was 263 at 5,750 rpm, a decrease of about 15 percent. Torque number variations were almost identical as well, with the maximum on gas measuring 307 pounds-feet at 4,750 rpm and 261pounds-feet at 5,000 on CNG, or a drop of about 18 percent.


System Awareness

The overall weight of our test truck was a bit on the heavy side at 7,400 pounds (with both tanks full), which isn’t likely to surprise anyone given the extra tank, mounting bracketry, extra plumbing and hoses, and external shielding included in the Westport conversion. The extra set of injectors and small mechanical changes in the engine do not amount to any significant weight addition. It’s worth noting that a system like this will require some special care, attention and understanding.

The system is fully warrantied from both Westport and Ford, but you can’t just fill the gasoline tank and never use it again, as much as you’d love to keep your gas tank full all the time. Generally speaking, many experts suggest not leaving gas unused in a tank for more than a few months. After that time, there could be significant degradation and oxidation that could reduce the effectiveness of the fuel in the combustion chambers as well as gum up or clog injectors. Westport suggests it would probably be good practice to run a tank of fuel through the truck every month or two. As long as you or your fleet manager can keep track of that, the lines and injectors should continue to work efficiently.

Fill-Up Experience

It may take consumers a little more time to get used to filling up the tank, especially since there are so few public-access CNG filling stations around. We live near one of the most densely populated metro areas in the country with 7 million people, and only 50 CNG fueling stations are within a 60-mile radius. And as you might guess, the numbers dwindle as you venture beyond the heavily populated areas and move across the country.  Clearly, the CNG infrastructure has a lot of improving to do, especially for long-trip use. For those suffering from range anxiety in any form, we have no doubt that’s exactly why so many of the new CNG vehicles you’re hearing about are looking to bifuel options to extend the range rather than limit it like some of the electric-only options do.

The station we used was locked behind a heavy gate that would open only with a working credit card that you slide into a card-reader box. Once inside, the pump nozzle fits onto the truck’s nipple flange that sits right next to the gas filler, inside the fuel door. Thankfully, all Super Dutys use the same extended fuel door that diesel-equipped trucks use to hold the diesel tank filler and diesel exhaust fluid filler. This turns out to be the perfect amount of room to put both a gas filler and CNG fitting.  

The CNG pump has a lanky set of tubes and a very un-ergonomic handle that mechanically clamps onto the nipple filler. Once it latches and starts pumping, there are whirs and groans and pops that make you fully understand what it means to push highly compressed gases through several small openings. It’s not difficult by any stretch, but the noises are a little unnerving. It took about four minutes to fill the 14 gallons, and the system tells you, both on a display screen and with a resounding clunk when the compressor shuts off, that you will not be putting any more fuel in this tank.

Disconnecting the handle is a little like what I imagine the NASA engineers have to do with the space shuttle right before they close the hatch on the astronauts, topping off the liquid nitrogen tanks. The small amount of CNG we could smell was not unpleasant, but there were warning labels all over the pumps that told us to evacuate the area if you sense any leak or impending ruptures.

Our first-ever CNG fillup took us about 20 minutes to get in and out of the station, but we did have to take a few photos and read through all the scrolling directions on the pump’s display.

Final Thoughts

To fill both tanks, we spent about $100, $75 of which was for almost 17 gallons of gasoline at Santa Barbara, Calif., prices (notoriously some of the most expensive in the state), with another $25 to fill up our single 18-gallon CNG tank. Under normal city and highway combined driving styles, we got about 130 miles on CNG before we went another 300 miles or so on gasoline before topping off again.

Calculated out on a per-mile basis, the CNG gave us 19.2 cents per mile, while the gasoline returned 25.2 cents per mile. Clearly, there are still some power, range and efficiency issues to work out with this type of alternative fuel system, but as a bifuel strategy, it worked pretty well for us.

We especially like the extra range; we like being able to watch the gas gauge sit at the “full” level for miles and miles; we really liked the CNG prices we found close by; and we liked the invisibility of the changeovers from CNG to gas.

Pricing for the commercial systems—which is mainly where they are being used—isn’t unreasonable, especially when you figure out your specific duty cycle and determine you’ll be making your money back in two, three or four years, depending on usage. However, if this is going to get popular with the regular truck-buying consumers, more access is going to be the most important factor. 


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