It seems like there's an unhealthy obsession with MPG in the Prius community. Anytime you modify a vehicle, there's likely going to be a change in your MPG. Just like Newtons Third Law, for every action there’s an equal and opposite reaction. “What will my MPG be after XYZ mod?” The fact is, you could have five different drivers in the exact same car, driving the exact same route, at the exact same time—and all five could end up with different MPG results.
For instance, the world record for MPG was just set in a 2024 Prius. Over the course of 3,300 miles, they achieved an impressive 79 MPG. What the heck, Toyota?! Why wasn’t I getting that kind of mileage in my stock 2024 Prius? Well, just like that driver managed to nearly double the claimed MPG, you could also end up with half of it by driving like a hormone-crazed teenager while your parents are out of town.
If you're that concerned with MPG, my advice is: leave your car stock. Or, if you’re feeling a little adventurous, install a lift to gain some clearance and stop there. Adding bigger or more aggressive tires, a high-clearance front bumper, a roof rack, ditch lights, etc., will almost certainly reduce your fuel economy. By how much? The possibilities are endless, and it’s impossible for us to give you a specific number.
So, if you're wondering how much your MPG will drop after installing 27" all-terrain tires, wheels carved out of solid blocks of lead, and a high-clearance metal front bumper, our suggestion is: leave your car stock. However, if you want to gain a whole lot of usability and ground clearance while sacrificing a little MPG, then we've got you covered. ;)