Every EarthRoamer XV-LT built since the original prototype in 2003 has been built on a Ford Commercial Duty truck chassis powered by a quiet, efficient and powerful turbocharged diesel engine. In addition, diesel fuel is used for camper heating, hot water heating and – using a ceramic diesel stove – cooking. It is probably obvious that we are huge fans of diesel fuel and diesel engines.

Why diesel?

When many Americans think of diesel they think of the slow, loud, trucks of yesteryear belching black smoke – but that is no longer the case.  With today’s modern diesel powered vehicles, nothing could be further from the truth. Today’s modern diesel engines are as quiet and clean a their gasoline counterparts. Diesel fuel is safer and more efficient than gasoline, and when it comes to efficiency, reliability, durability and power, diesels engines are the hands down winner over gasoline engines.

Diesel Fuel vs. Gasoline

Energy Content per Gallon

Diesel fuel has a higher energy density than gasoline. One gallon of diesel contains approximately 147,000 BTUs of energy, while a gallon of gasoline only has 125,000 BTUs. This means it takes more gasoline to equal the power output of diesel, making diesel engines more efficient per gallon of fuel burned.


Diesel fuel is safer than gasoline. Although diesel fuel will burn in open air using a wick, it will not explode and does not release a large amount of flammable vapor. The low vapor pressure of diesel makes diesel engines immune to vapor lock.

Diesel vs. Gas Engines

Fuel Economy

Diesel engines burn less fuel than a gasoline engine performing the same work due to the diesel engine’s higher combustion temperature and greater expansion ratio. Gasoline engines are typically only 30% efficient while diesel engines can convert over 45% of the fuel energy into mechanical energy.

Also, because diesel engines use the more efficient direct fuel-injection method (fuel injected directly into cylinder) compared to the port fuel-injection setup in gas engines where gas is mixed with incoming air in the intake manifold, the diesel system has little wasted or unburned fuel.

Finally, Diesel engines can accept turbo-charging pressure without any natural limit, dramatically increasing both efficiency and power. Gasoline engines in contrast inevitably suffer detonation at higher  pressure.

Owners of 2011 and newer EarthRoamer XV-LTs have reported mileage in the 11-12 mpg range in highway driving. While 11 mpg might not initially sound that impressive, many RVs and expedition vehicles are lucky to achieve half of that mileage. When weight is taken into consideration, the 11 mpg of an EarthRoamer is very impressive. For example, a 2,672 pound Honda Civic that gets 39 mpg would have to get over 65mpg to match the fuel efficiency per pound of a 16,000 pound EarthRoamer XV-LT!

Diesels also use about one third as much fuel at idle as gasoline units and the 6.7 liter ford PowerStroke only burns about .5 gallons of diesel fuel per hour at idle.

Maintenance, Reliability and Long-Term and Durability

Diesel engines have no high voltage electrical ignition system, resulting in high reliability and easy adaptation to damp environments. This means there are no spark plugs to replace and no ignition system component to service.

The diesel engine found the Ford F-550 can be thought of as “mini big-rig engine,” with corresponding low maintenance costs and long term reliability. Due to the increased strength of parts used to handle high combustion pressures of a diesel engine and the better lubrication properties of diesel fuel, Diesel engines last much longer than comparable gasoline engines. The average gas engine is good for only around 125,000 miles before needing a rebuild and isn’t designed to constantly pull a heavy load. A diesel engine can typically go  2-3 times this amount before needing an overhaul.


Because of the relatively high-compression ratio necessary to ignite diesel fuel (17:1 diesel versus 9:1 for gas), diesel engines make torque and power low in the RPM range. The torque advantage of diesels is perfectly suited for pulling heavily loaded EarthRoamer Xpedition Vehicles up steep grades.