Choosing Between Gas and Diesel?

Counting the cost

When it comes to truck engines, there are two primary fuel choices (at least until electric vehicles become more mainstream and powerful): diesel vs. gas. Whether you’re driving a Ford, Chevy, or Dodge, eventually the discussion will turn to engine types.

How do you choose the one that’s right for you? How do you determine the real cost differences between the two? Whether you’re buying a truck for work, to tow a boat or RV, or to haul camping gear into the mountains, you’ll have to decide between a gas and diesel engine.

Initial cost

When you start shopping, generally speaking, you’ll see that diesel vehicles cost much more than their gas equivalents. A Duramax diesel-equipped Chevy 2500 will cost a full $11K more than the Vortec powered 6.0L V-8. Other manufacturers offer similar costs for the diesel upgrades.

It should also be noted that most often diesel engines are offered on heavier duty trucks, with a few exceptions. These trucks often cost more initially because they offer different suspensions and drivetrain components.

The key is to know if you need the heavier duty model with the higher payload and towing capacity numbers, or if the lighter duty gas model is sufficient for your needs. However, there are other costs to consider beyond the initial costs of a diesel engine.

Fuel economy

Diesel engines in passenger cars offer a significant fuel mileage advantage over gas engines. However, truck engines are an entirely different story. The difference between gas and diesel trucks is an average of 2 miles per gallon under normal driving conditions.

Where the real difference comes is in situations where you’re towing or hauling, especially if you’re driving long distances when doing so. The difference can extend to 8-10 miles per gallon.

In a Government Fleet article titled “Gas vs. Diesel: The Bad Investment Only Fleet Managers Know About” the author discusses this in depth. Fleet managers purchasing diesel engines for the fuel savings are making a critical mistake. In fact, the high cost of diesel fuel often negates any gains in mileage.

In fact, if short distances are traveled, and trucks have to idle often in traffic, diesel engines are actually far costlier to operate. Most of the time, load and towing requirements can be met with gas equivalent vehicles.

However, fuel mileage alone is not a slam dunk for gas ownership over diesel. There are other factors and situations to consider.

Power

While for many purposes, gas vehicles can meet your needs. But there are times when they simply won’t. For towing heavy trailers, constant hauling over distances, and frequent hill climbing, the added torque available in diesel motors is extremely desirable and often a necessity.

This is because diesel engines can take more turbo boost than their gas counterparts. A 15-psi boost is considered to be high for a gas engine, in a diesel, 15-30 psi is normal, and 30-50 is not uncommon from aftermarket turbos. Also, diesel fuel by nature contains 11% more energy than a gallon of gas.

The piston stroke length is another reason these engines can produce so much power off the line. This is because diesels operate at much lower RPM than gas engines, redlining much sooner. The longer stroke means the piston travels slower, and the crankshaft does not need to turn as fast.

A diesel quite simply has a higher capacity to produce torque than a gas motor. If you need towing power and hauling power off the line, a diesel is the right choice for you.

Maintenance costs

The total cost of ownership is the best way to figure out if a truck is a good value. Are repairs on a diesel cheaper than those on a gas engine? Not really. Hard parts like starters, alternators, water pumps, and others are actually more expensive in a diesel, but less likely to fail. Diesel parts tend to last longer, but when they do break, they cost more to replace.

The same is true for oil changes. While they come less frequently in a diesel motor (great if you’re traveling across the country), they cost nearly double that of conventional oil changes due to higher oil capacity and higher filter costs. Belts and hoses tend to be costlier as well, and cleaning air filters rather than replacing them is often the better solution.

While it’s hard to offer definitive figures, maintenance costs are usually a wash. Gas vehicles need maintenance more often, but it’s cheaper. Diesel maintenance intervals are further apart but costlier. The bottom line is how you’ll use the truck, and if you need the extra power offered by a diesel.

Which is right for you, gas or diesel? Only you can answer that. While initial costs are higher, maintenance, repair and fuel costs come out about the same in the long run.

If you need the power a diesel can produce, if you drive a lot of miles and want an engine that will last longer, a diesel is probably worth the extra initial cost. If you can accomplish what you need to with a gas motor, and drive shorter distances rather than longer ones, a gas engine is probably your best option.