There are many reasons to consider a diesel engine, including fuel economy. Diesel engines typically deliver 25% to 30% better fuel economy, but you also need to factor in the cost differential between gasoline and diesel. In the heavy-duty segment, diesel take rates are high because of capability and fuel economy benefits.

The experts at the Diesel Technology Forum recently reviewed the three major brands and weighed in about how they compare to each other.

Ram Truck recently introduced a diesel option in the 1500 that promises to deliver improved fuel economy, an important feature in the half-ton segment. “It’s interesting to see the shift,” says Mike Cairns, head of Ram Truck engineering. “With fuel economy in the light-duty segment as the driving force of change and new technology available, smaller diesel engines can deliver on both efficiency and capability.”

Brian Rathsburg, Super Duty marketing manager for Ford, cautions that the fuel economy advantage can be hard to quantify due to the many different pickup configurations available. “But if you are in the F-250 portion of the lineup and you have a diesel and are not towing heavy loads or driving at altitude, you can get north of 20 mpg. On a similarly equipped gasoline truck, it could be in the 15- to 17-mpg range. So it is not uncommon for these customers to see 3- to 5-mpg higher fuel economy with a diesel.”

The gap widens further when you’re towing a heavy load. “Diesel engines run more efficiently at high capacities,” says Rathsburg. “On similarly equipped vehicles towing the same amounts, you will get better fuel economy on the diesel engine than you would on the gasoline engine.”

However, the decision of gas or diesel is often based more on capability than fuel economy. That’s why you see a majority of heavy-duty pickups equipped with diesels.

Consider the Ford Super Duty pickups. “About 60% of our mix is diesel engines and the other 40% are gas engines,” notes Rathsburg. “For those 40% who buy a gas truck, they want the utility of a heavy-duty truck, but they may not need the extreme amount of capability that the diesel gives them. As a result, they can’t justify the $8,000 to $9,000 price premium. They may need to haul 3,000 or 4,000 lbs. of equipment in the pickup box and not have a lot of need for towing. Those are the types of usage profiles where we see gas buyers.”

“Ram Heavy Duty trucks have nearly an 80% take rate on the Cummins diesel, where the No. 1 ‘why buy’ is capability,” says Cairns. “Our new 6.4-liter HEMI gas engine closes the capability gap and gives customers who may not require a huge GCWR another option.”

The power characteristics between gas and diesel are quite different. Gasoline engines run at higher rpm and typically produce more horsepower, while diesel engines turn at lower engine speeds and produce more torque.

“When you go from gas to diesel in an HD (heavy-duty pickup), you usually double your torque,” says Tom Wilkinson, Chevrolet Communications. For instance, the Chevrolet Silverado and GMC Sierra 2500 use the Duramax 6.6-liter diesel engine that pumps out 397 hp at 3,000 rpm and 765 lbs.-ft. at 1,600 rpm. This compares to the 6.0-liter Vortec V8 that is rated at 360 hp at 5,400 rpm and 380 lbs.-ft. of torque at 4,200 rpm.

Such results are similar across the product offerings of all heavy-duty pickup brands.