Welcome back. You might expect a newer SUV to close the gap with a sedan on the highway, but the basics still work against it.

If you compare two vehicles with similar engines, the taller and heavier one usually burns more fuel at steady speed. A compact sedan and a compact SUV can share a lot on paper, including engine size and transmission, yet the highway numbers still separate once you get up to speed and hold 60 or 70 mph.

At city speeds, stop and go traffic puts a lot of stress on acceleration. On the highway, air becomes the bigger issue. An SUV usually sits taller and presents more front area to the air than a sedan does. That means the engine has to keep pushing against more drag for mile after mile. A clear example is the difference between a low four door car and a taller crossover built on the same platform. Even when their drivetrains match, the crossover generally posts a lower highway fuel economy figure because its shape asks more from the engine once speed stays high.

You may think weight matters most when you pull away from a light, but it still matters on the highway. SUVs often carry extra mass from a taller body structure, bigger wheels, reinforced suspension parts, and available all wheel drive hardware. That added weight increases rolling resistance and makes the powertrain work harder on grades and during passing. The gap is easy to see in pairs from the same brand. A sedan based on a midsize platform usually comes in hundreds of pounds lighter than the SUV version, and that difference keeps affecting fuel use even after cruising speed settles in.

A lot of people focus on the engine, but tires do a quiet share of the work. SUVs often use wider tires and taller ride height settings, both of which can hurt efficiency. Wider tires increase contact with the road and usually raise rolling resistance. Ride height also affects airflow underneath the vehicle, and that underbody airflow is rarely as clean as what you get with a lower sedan. If you look at efficiency focused cars, many of them use narrower tires, smoother undertrays, and a lower stance for exactly this reason.

Not every SUV has all wheel drive, but many do, and that adds hardware. A transfer case, extra driveshafts, and rear drive components all create small mechanical losses. Each one may seem minor on its own, but together they trim efficiency. A front wheel drive sedan avoids much of that extra drag in the drivetrain. Even among SUVs, the front wheel drive version often returns better highway mileage than the all wheel drive version with the same engine, which gives you a clean apples to apples example of how the extra parts affect fuel use.

Automakers do a lot to narrow the gap. They use turbocharged small engines, 8 speed and 10 speed transmissions, cylinder deactivation, and active grille shutters. Those tools help, and some modern crossovers are much closer to sedans than older truck based SUVs were. But they do not erase the basic disadvantages of shape, mass, and ride height. If two vehicles share similar technology, the lower and lighter one still has an easier job on the highway. You can see that across many lineup pairs where the sedan keeps a stronger highway rating despite using the same family of engine.

If you want lower highway fuel use, the most useful question is not just engine size. Check body shape, curb weight, tire width, and whether the vehicle has all wheel drive. Those details tell you more than the badge on the back. So if you're wondering why an SUV drinks more fuel than a sedan at highway speed, the answer is usually simple, the SUV is pushing more air, carrying more mass, and turning more hardware every single mile.