- Each 1 PSI of underinflation reduces fuel economy by approximately 0.1–0.3%, according to DOE data.
- Tires underinflated by 10 PSI can reduce fuel economy by 1–3%, costing an extra $50–$100 per year.
- NHTSA estimates that about 1 in 4 vehicles on U.S. roads has at least one significantly underinflated tire.
- Proper tire inflation is the single easiest maintenance step drivers can take to maintain fuel economy, per the DOE.
01 Rolling Resistance and Tire Pressure
Each 1 PSI of underinflation reduces fuel economy by roughly 0.1% to 0.3%, according to DOE data, and tires underinflated by 10 PSI can cut fuel economy by 1% to 3%. Tire pressure affects fuel economy primarily through rolling resistance—the energy lost as the tire flexes and deforms while rolling. An underinflated tire has a larger contact patch with the road surface, which increases the deformation of the tire sidewall and generates more heat. The engine must work harder to overcome this additional resistance.
DOE, Office of Energy Efficiency & Renewable Energy, "Tire Pressure and Fuel Economy"; ORNL, Transportation Energy Data Book, Chapter 4At typical highway speeds, rolling resistance accounts for approximately 20–30% of total driving resistance (with aerodynamic drag accounting for the rest). At lower city speeds, rolling resistance becomes the dominant factor, representing 50–70% of resistance. This means tire pressure has a proportionally larger effect on city fuel economy than highway fuel economy.
ORNL, Transportation Energy Data Book, Edition 41, Table 4.28: Vehicle Road Load Forces by speed02 Fuel Economy Impact by PSI
The DOE has quantified the relationship between tire pressure and fuel economy. The general guideline is that for every 1 PSI all four tires are underinflated below the recommended pressure, fuel economy decreases by approximately 0.1–0.3%. The table below illustrates the cumulative effect.
DOE/EPA, fueleconomy.gov, "Keeping Your Car in Shape": tire pressure fuel economy impact| Underinflation (all 4 tires) | FE Reduction | MPG at Baseline 28 MPG | Extra Gallons/Year |
|---|---|---|---|
| Properly inflated | 0% | 28.0 | 0 |
| −5 PSI | −0.5 to 1.5% | 27.6–27.9 | 2–6 |
| −10 PSI | −1.0 to 3.0% | 27.2–27.7 | 4–13 |
| −15 PSI | −1.5 to 4.5% | 26.7–27.6 | 6–19 |
| −20 PSI | −2.0 to 6.0% | 26.3–27.4 | 9–26 |
03 Annual Cost of Underinflation
The DOE estimates that the average driver who does not regularly check tire pressure wastes approximately $50–$100 per year in excess fuel consumption. This estimate is based on NHTSA survey data showing that about 25% of passenger vehicles have at least one tire underinflated by 8 PSI or more.
NHTSA, "Tire Pressure Special Study" and TPMS effectiveness reports; DOE fuel cost estimates| Vehicle Type (MPG) | Annual Gallons (correct PSI) | Extra Gal (−10 PSI) | Extra Cost/Year |
|---|---|---|---|
| Compact car (33 MPG) | 364 | 4–11 | $13–$36 |
| Midsize sedan (28 MPG) | 429 | 4–13 | $13–$43 |
| Midsize SUV (26 MPG) | 462 | 5–14 | $17–$46 |
| Pickup truck (20 MPG) | 600 | 6–18 | $20–$59 |
Beyond fuel costs, underinflated tires also wear faster and unevenly. NHTSA data shows that tires consistently run 10 PSI below recommended pressure can lose up to 25% of their tread life, potentially costing hundreds of dollars in premature tire replacement.
NHTSA, "Tire Safety: Everything Rides on It"; DOT tire wear study dataEstimate your vehicle's driving cost using official EPA fuel economy data.
Use the Calculator04 Seasonal Pressure Changes
Tire pressure changes with ambient temperature. According to the DOE and tire industry data referenced by NHTSA, tires lose approximately 1 PSI for every 10°F drop in temperature. This means a vehicle with properly inflated tires in September (70°F) could be 5–8 PSI underinflated by January (20–30°F) without any leaks or damage.
DOE/EPA, fueleconomy.gov, "Keeping Your Car in Shape: Tire Pressure"; NHTSA, TPMS guidance documents| Temperature Change | Pressure Change | Example (set at 35 PSI in 70°F) |
|---|---|---|
| 70°F (baseline) | 0 PSI | 35 PSI |
| 50°F (−20°F) | −2 PSI | 33 PSI |
| 30°F (−40°F) | −4 PSI | 31 PSI |
| 10°F (−60°F) | −6 PSI | 29 PSI |
This seasonal effect compounds with the cold-weather fuel economy penalties documented by the DOE. In winter, a vehicle may be simultaneously losing fuel economy from cold engine operation, thicker lubricants, and underinflated tires—all factors that reduce MPG in cold weather.
05 DOE Recommendations
The DOE and NHTSA provide clear guidelines for maintaining proper tire pressure:
DOE/EPA, fueleconomy.gov, "Keeping Your Car in Shape"; NHTSA, "Tire Safety" consumer guidance- Check pressure monthly and before long trips. The DOE recommends using a quality gauge rather than relying on visual inspection, as tires can be significantly underinflated before appearing low.
- Use the vehicle placard pressure, not the tire sidewall maximum. The recommended pressure is listed on a sticker on the driver’s door jamb or in the owner’s manual. The number on the tire sidewall is the maximum pressure, not the optimal pressure.
- Check when tires are cold (driven less than 1 mile or sitting for 3+ hours). Driving heats the tires and increases pressure by 2–4 PSI, which gives a misleadingly high reading.
- Include the spare tire in monthly checks. A flat spare when you need it creates both a safety hazard and potential towing costs.
All passenger vehicles sold in the U.S. since 2007 are required to have a Tire Pressure Monitoring System (TPMS) that alerts the driver when any tire is 25% or more below recommended pressure. However, NHTSA notes that a 25% threshold means the system does not alert until tires are already significantly underinflated—regular manual checks remain important.
NHTSA, Federal Motor Vehicle Safety Standard 138 (FMVSS 138): TPMS requirements; 49 CFR Part 57106 Data Sources
- DOE/EPA: FuelEconomy.gov – "Keeping Your Car in Shape." fueleconomy.gov
- NHTSA: Tire Pressure Monitoring System (TPMS) regulations and reports. nhtsa.gov
- ORNL: Transportation Energy Data Book, Edition 41, Chapter 4. tedb.ornl.gov
- EIA: Weekly Retail Gasoline Prices. eia.gov