RAM 2500 CNG Truck

"Reduced costs, same performance, reduced emissions, crash compliant"

RAM 2500 CNG Truck                              
By: Police Fleet Manager Staff                    

RAM is now producing the industry’s only OE-built, bi-fuel pickup: the 2500 CNG. At its 2013 launch, the CNG-powered RAM pickup is available one way: 2500 Heavy Duty, Crew Cab, 4x4, 5.7L HEMI® V8, 66RFE 6-speed automatic transmission. The bi-fuel truck is available in two trim levels: ST and SLT. The SLT trim truck uses an electronic part-time transfer case: 2WD, 4LOCK and 4LOW.

The RAM 2500 CNG is not a dedicated CNG vehicle. Instead, it is a true bi-fuel vehicle. Most importantly, it is a FACTORY bi-fuel truck, the only such OE-built pickup. This is not an aftermarket or nearby Tier One supplier CNG conversion. The RAM 2500 CNG is built on the same production line in Saltillo, Mexico as the rest of the RAM 2500 trucks. The RAM 2500 CNG is made entirely in-house, on the same assembly line with the other diesels and the HEMIs. The CNG system is built at the factory and it leaves the assembly plant with CNG in the tanks.

Federal Crash and Safety Compliant

Of maximum significance, as an OE vehicle, the RAM 2500 CNG passes all of the NHTSA crash tests required of any OE factory vehicle. Aftermarket conversions raise safety issues, or at least they certainly should. This is one CNG-powered truck that is fully compliant with all federal crash and safety regulations. That sets the RAM 2500 CNG apart from every other CNG-powered truck, period.

Most aftermarket bi-fuel conversions, either CNG or propane, are simple installations. Crash tests are way too expensive for the typical aftermarket company to have performed. Even more, crash and safety tests must be performed on every variation of the vehicle installation: 2WD, 4x4; standard cab, extended cab, 4-door cab. Those compliance tests just aren’t done by the average CNG tank upfitter.

CNG Burn Compliant Engine

NHTSA crash and safety tests are just one slam-dunk advantage of the RAM factory option over an aftermarket conversion. A second slam-dunk advantage involves internal engine components. There is more to a successful, durable, reliable bi-fuel vehicle than tanks, pipes, valves and flashing the engine control module. The internal components of the gasoline engine must be upgraded to handle the different burning characteristics of CNG.

The 5.7L HEMI V8 used in the RAM 2500 CNG has been modified to accommodate burning CNG. During ignition, CNG provides much less upper cylinder lubrication than gasoline, and this leads to premature valve wear. The reworked heads, valves and spark plugs are different; the valve seats are harder; and the engine gets a CNG-specific fuel rail with dedicated injectors. (You don’t get CNG-compatible heads and valves with the typical aftermarket CNG conversion.) The powertrain control module is also recalibrated for CNG, which is between 110 and 130 octane.

Starts on Gasoline

At temps below 50 deg F, the RAM 2500 CNG will (probably) start on gasoline and then automatically switch to CNG. Both ambient temps and engine coolant temps factor into the fuel-at-start decision. In fact, the truck may simply start and run on CNG. If it starts on gas, after the coolant reaches about 130 deg F, which is between two and four minutes of run time, the engine controller switches from gasoline to CNG. The truck continues to use CNG until the twin tanks are empty, then the truck smoothly transitions to gasoline.

The RAM 2500 CNG will give priority to the cleaner, less expensive CNG and run on CNG until the tanks are empty. If there is CNG in the tanks, the truck will burn that first, and then go to gasoline. The driver cannot, for example, burn gasoline in a rural area and easily switch to CNG in an urban area. The driver can, however, stop the truck, open the CNG tank access cover in the bed, and manually rotate the master shutoff valve to turn off the CNG flow.

Totally Smooth Transition

The dash display on the RAM 2500 CNG has two fully integrated, factory fuel gauges—one for gasoline and one for CNG. No tacky add-on gauges from an aftermarket conversion. In addition to the fuel gauges, the message center also clearly displays whether the truck is operating on CNG or GAS. An amber low fuel light is also clearly labeled as CNG or GAS.

The switch back and forth between gasoline and CNG is absolutely seamless and transparent. You cannot feel it and you cannot hear it, even if you are closely watching the message center to see the display change. The switch between CNG and gasoline is smooth and quiet. You simply cannot tell. Unlike some aftermarket conversions, the driver does not have to manually switch between the gasoline tank and the CNG tanks.

CNG is not LPG

CNG (compressed natural gas) is very different from LPG (liquefied petroleum gas). LPG may be more commonly known as propane. CNG is made of methane and ethane, and is lighter than air. LPG is made of propane and butane, and is heavier than air.   

The CNG is stored in twin, high-pressure tanks bolted to the front of the bed. The tanks and associated piping and valves are protected under a heavy-gauge steel cover ribbed for rigidity. The steel container is flush with the top of the bed and contains an access panel to the CNG valves.

The fill receptacle for both the gasoline and the CNG are behind the same fuel fill door. Connecting the CNG fill nozzle is extremely easy. Rotate the external lever one way on the pump nozzle to open the clamp jaws, place the nozzle over the CNG receptacle, and rotate the lever the opposite direction to close the clamp jaws. Lift the pump lever just like you do a gasoline pump and in goes the CNG under 3600 psi pressure. The time to fill the 18.2-gallon equivalent CNG tanks is about the same time as to fill the 32-gallon gasoline tanks.

Short Bed

In the 8-foot bed, the CNG tanks take up 39 inches (3 ¼ feet) leaving 57 inches (4 ¾ feet) for cargo. Those high-pressure, submarine-hull CNG tanks have to go somewhere. The resulting 4 ¾-foot usable bed is quite short, but the heavy-gauge steel enclosure over the CNG tanks will support some weight. At any rate, keep the shorty-short bed in mind as you consider how to best use this truck. The RAM 2500 CNG may tow what you expect of a ¾-ton truck, but it will certainly not haul a typical ¾-ton cargo.

That said, the RAM 2500 CNG has lower tow/haul ratings than a comparable RAM 2500. The gasoline-only RAM 2500 can haul up to 2,360 pounds and tow up to 14,550 pounds. The RAM 2500 CNG can haul up to 1,580 pounds and tow up to 7,650 pounds.

Driving Impressions

The RAM 2500 CNG is a big truck. If you are used to thrashing about in ½-ton trucks, the ¾-ton truck seems long and feels like it has a wide turning circle. The RAM 2500 CNG is a Crew Cab with an 8-foot bed and a 168.9-inch wheelbase. It has a 30-inch longer wheelbase and a 4-foot wider turning circle (49.2 feet) than the ½-ton RAM 1500 Special Service. Of course, the RAM 2500 CNG needs the full 8-foot Long Bed to hold the twin CNG tanks and provide at least a little cargo/haul room.

The big RAM is much more at home in suburban, rural and highway driving where the long overall length and wide turning diameter simply don’t matter. During urban and heavily urban driving, the long ¾-ton truck is not so easy to maneuver.

For those officers who have had lots of experience with ½-ton trucks, the RAM 2500 CNG rides and drives very differently from the average ½-ton. The new RAM 1500 uses a coil-spring rear suspension. It rides and drives like a sedan with a sport suspension. The RAM 2500 uses a multiple-leaf rear suspension. It rides and drives like the ¾-ton truck that it is. Jack-be-nimble it is not, but no ¾-ton truck is.


The 5.7L HEMI V8 makes the RAM 1500 4x4 Crew Cab a real hot rod. The 2012 RAM Special Service package pickup hit 60 mph in just 7.0 seconds. A similar 5.7L V8 in the RAM 2500 CNG is not quite so fast for two reasons.

All else equal, the RAM 2500 Crew Cab Long Bed is about 1,300 pounds heavier than the RAM 1500 Crew Cab Standard Bed. Second, the factory CNG conversion adds about 750 pounds to the RAM 2500. That said, the 5.7L HEMI V8 is enough engine for nearly all driving uses and tow/haul tasks required of any ¾-ton truck.

The 5.7L V8 is rated at 383 hp and 400 lb-ft of torque when running on gasoline. When using CNG, the engine produces about 15 percent less power and 10 percent less torque. For example, the RAM 2500 hit 60 mph in 10.5 seconds using CNG and 60 mph in 9.8 seconds using gasoline…pretty good for a 7,540-pound (curb weight) pickup.

However, if the truck is operating in CNG fuel mode and maximum torque is required from the engine, such as towing/hauling at maximum GVW up a substantial grade, the ECM will automatically switch the fuel mode from CNG to gasoline to take advantage of the more denser fuel, offering greater torque. Under nearly all driving conditions, we found it very hard to tell the difference in driveability between gasoline and CNG.

Same Fuel Economy

The RAM 2500 CNG gets about the same fuel mileage on CNG as it does on gasoline. Actually, it may get better mileage on the higher octane CNG. In the “green fever” with E85, “they” forgot to tell us that the mileage when using E85-ethanol would be worse than gasoline, a lot worse—like 15 to 25 percent lower fuel economy and E85 was never 25 percent cheaper than gas. Not so with CNG and the pricing in gasoline gallon equivalent.

We put over 1,800 miles on the RAM 2500 CNG, including 750 miles using CNG. Our driving conditions were admittedly best-case for fuel economy: lightly loaded, 75 mph interstate cruising, no A/C. We averaged 12.7 mpg on gasoline and 13.7 mpge on CNG. No, the average ¾-ton special service or municipal truck would never be driven this way. However, the official RAM driving ranges are based on 14 mpg!

The total estimate driving range for the RAM 2500 CNG based on the 18.2-gallon CNG tank and the standard equipment 8.0-gallon gasoline tank is 367 miles. That is 255 miles from the CNG. With the optional 32-gallon gasoline tank, the combined total range is estimated at 703 miles.

Under absolutely ideal fuel economy driving conditions, we can mostly confirm those published driving range numbers. Three times we reached 655 miles, combined. That said, under more typical ¾-ton truck use, more common tow/haul use, expect half that range. Even still, something over 300 miles is a pretty good driving range for a green initiative, ¾-ton truck. 

8-gallon or 32-gallon?

The RAM 2500 CNG comes standard with an 8-gallon gasoline tank. A 32-gallon gasoline tank is optional. The 8-gallon “reserve” tank puts a real emphasis on actually using CNG where the infrastructure is in place and the driving is somewhat localized. The 32-gallon tank, however, gives the maximum driving range often demanded of ¾-ton truck tasks. It is the difference between a 367-mile maximum CNG and GAS combined range (8-gallon tank) and a 703-mile maximum CNG and GAS combined range. Unless your ¾-ton fleet is on a very short leash, get the 32-gallon tank.

CNG Payback

Unlike most “green” solutions, the CNG option pays for itself well within the normal service life of the vehicle. When we tested the RAM 2500 CNG, the national average price for CNG was $2.10 per gallon equivalent. At the same time, the national average price for unleaded regular gasoline was $3.45 per gallon. CNG was 39 percent less expensive than gasoline or gasoline was 64 percent more expensive than CNG, whichever way you want to look at it. We averaged 13.7 mpge using CNG and 12.7 mpg on gasoline.

The cost of the CNG option is an eyebrow-raising $11,000. Yet, doing the math, the much less expensive fuel and slightly better fuel economy pay for the CNG option in 93,000 miles. On a ¾-ton truck, that is just a half-life.

It will probably be more economical than that; probably pay for itself sooner. Our fuel mileage was based on lightly loaded, freeway cruising. Instead, if you use the vehicle like a ¾-ton truck—towing and hauling—and in urban, suburban and rural use, the fuel economy will be half of the interstate cruising. At 7 mpg for both CNG and gasoline, the CNG conversion payback is just 57,000 miles.

Obviously, any use of gasoline extends the payback period. You lower operating costs every single mile you run on CNG. Look at it a different way. With CNG 39 percent less expensive than gasoline, it is like getting 64 percent better mileage on gasoline. So, if you get 13 mpg on gasoline, it is like getting 21 mpg—from a ¾-ton truck!


Production of the RAM 2500 CNG began in October 2012. RAM made their biggest 2500 CNG delivery to date in March 2013 with a shipment of 242 trucks to the Oklahoma Department of Transportation. Oklahoma is the home of domestic CNG production. The ODOT is using the RAM 2500 CNG as highway service trucks.

For your ½-ton truck tow/haul tasks, think of the RAM 2500 CNG as a way to achieve your department’s green initiatives with a vehicle far more durable and rugged than any ½-ton truck…with operating costs way less than any ¾-ton truck.

Published in Police Fleet Manager, Sep/Oct 2013

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