Does Tire Size Affect Fuel Economy?

The Problem with Unsprung Weight

Tires are classified as "unsprung weight"—meaning they are components not supported by the vehicle's suspension. Every pound of rotating, unsprung weight requires significantly more engine horsepower to accelerate and brake compared to weight sitting inside the vehicle.

Moving from a highway tire (weighing 38 lbs) to an aggressive Light Truck (LT) mud-terrain (weighing 65 lbs) requires your engine to fight physics at every stoplight. The harder your engine pushes, the more fuel it burns.

Rolling Resistance

Tire size dictates the contact patch. A wider tire puts more rubber on the ground. More rubber creates more friction. This is known as "rolling resistance." While fantastic for off-road crawling, that massive friction is terrible for cruising down the interstate. Your vehicle has to constantly overcome the grip of aggressive tread blocks, tanking your highway fuel efficiency.

Real-World MPG Differences

Let's look at a real-world scenario. Let's take a factory Jeep Wrangler averaging 19 MPG on stock 31-inch tires. If that owner upgrades to a 35-inch mud-terrain tire, they can easily expect their fuel economy to drop to 14 MPG. Over the course of 15,000 miles driven per year, that minor tire upgrade could cost the owner an extra $800+ purely in gasoline.

Mitigating the Loss

If you want to size up but save gas, avoid heavy "E-load" 10-ply tires. Stick to Standard Load (SL) or C-load tires. Secondly, seek out less aggressive All-Terrain (A/T) patterns instead of deep-lug Mud-Terrains (M/T).

Calculator Integration

Use our TireFitPro calculator to compare tire sizes and check if they will fit your vehicle without rubbing or speedometer issues. Keep major size jumps to a minimum to save at the pump!