The real reason diesels keep going long after gas engines give up

Diesel pickups and SUVs tend to live longer than their gasoline siblings. Here's what actually makes the difference, and when the premium isn't worth paying.

Diesel engines in pickups and large SUVs are often considered more durable than gasoline ones. That doesn't mean any diesel will automatically outlast any gasoline engine, but under equal conditions it does have several built-in advantages.

One example is the 3.0-litre inline-six Duramax LZ0 that GM uses in Chevrolet and GMC trucks. The same models can be ordered with a gasoline V8, and that side-by-side comparison shows the difference in approach particularly well.

The first factor is the fuel itself. Diesel has better lubricating properties and higher viscosity than gasoline. It doesn't replace engine oil, but it helps reduce friction in fuel-system components and clings to metal surfaces better. Gasoline simply doesn't behave that way.

The second point is how the engine works. A diesel doesn't need a spark plug — the mixture ignites under compression. To achieve that, the engine runs at a much higher compression ratio, which means it has to be built tougher from the start. The block, cylinders, crankshaft and other components have to handle serious loads.

Diesel engines usually have a longer piston stroke and lower operating revs. They don't spin as high as gasoline units, but they deliver more pull at low rpm. Fewer revs means fewer wear cycles over the same running time. For a heavy pickup that tows trailers or eats up highway miles, that's a strong argument.

There's a flip side. A diesel costs more upfront, and its reinforced components and high-pressure fuel system can be noticeably pricier to repair. Maintenance can't be delayed either: bad oil, low-quality fuel or problems with the emissions aftertreatment system quickly turn that longevity advantage into an expensive headache.

Fuel economy, on the other hand, often favours the diesel. A Duramax-powered Chevrolet can deliver around 9.4 l/100 km in combined driving, while the gasoline V8 sits closer to 13.8 l/100 km. Even factoring in the higher price of diesel fuel, the gap can add up over several years.

Diesel isn't for everyone. If the car barely gets driven, lives on short trips and never works hard, the premium may never pay off. But for high mileage, highway runs, towing and heavy-duty work, that built-in durability is still the very reason buyers put up with the price and the more complex servicing.