Tire Pressure and Fuel Economy: What Agencies Say (and How to Estimate Cost Impact)
- FuelEconomy.gov reports underinflated tires can lower gas mileage by about 0.3% per 1 psi drop in average tire pressure.
- The same page notes many vehicles have at least one underinflated tire, and links to NHTSA materials.
- You can estimate cost impact using cost-per-mile math, then verify with your own mileage logs.
What We Know (Sourced)
FuelEconomy.gov states that underinflated tires can lower gas mileage by about 0.3% for every 1 psi drop in the average tire pressure. It also notes that many vehicles have at least one tire significantly underinflated and links to NHTSA materials about tire pressure monitoring and tire safety.
FuelEconomy.gov's cold-weather page highlights that cold temperatures are associated with lower fuel economy and lists keeping tires properly inflated as a practical step.
NHTSA has published materials on TPMS and tire safety that reinforce why pressure checks are a routine part of safe vehicle operation.
How Underinflation Affects MPG (Conceptually)
When a tire is underinflated, it typically deforms more as it rolls. That increases rolling resistance, which means the engine (or motor) must do more work to keep the vehicle moving at the same speed. More work means more energy — and that energy ultimately comes from fuel or electricity.
Even if the MPG impact sounds small, it can compound with other "small losses" like unnecessary roof drag, aggressive acceleration, and idling. Related: roof racks and MPG and aggressive driving.
How to Estimate the Cost Impact
There are two clean ways to estimate the financial impact:
Method A: Use the 0.3% per psi baseline (rough estimate)
Then translate the MPG change into dollars using cost-per-mile math:
- Cost per mile (fuel) = price per gallon ÷ MPG
- Annual fuel cost = annual miles × cost per mile
Related: cost per mile formula.
Method B: Measure before/after with the same route
If you want the most accurate answer, measure MPG for a few tanks at your current pressure, then correct pressure to the placard value and measure again. Keep your route and driving style as consistent as possible so you isolate tire pressure as the variable.
| Step | What to do | Why it matters |
|---|---|---|
| Baseline | Log MPG for 2–3 fill-ups | Smooths day-to-day noise |
| Correction | Set all tires to placard PSI | Defines your "optimized" baseline |
| Re-test | Log MPG for 2–3 more fill-ups | Shows real effect for your car and route |
A Simple Tire-Pressure Routine
- Check monthly and before long trips.
- Check when tires are cold for consistent readings.
- Use placard PSI (doorjamb), not the sidewall maximum.
- Expect seasonal drift and plan to re-check during cold snaps. Related: cold-weather tire pressure.
What's Next
- If your goal is cost reduction: compute a rough estimate, then run a before/after measurement for 4–6 fill-ups.
- If your goal is trip reliability: check pressure before road trips and keep a small portable inflator in the vehicle.
- If you're seeing repeat warnings: investigate leaks and don't assume it's only weather.
To put tire pressure in the broader context of winter efficiency, see: fuel economy in cold weather.
Frequently Asked Questions
Is the 0.3% per psi number exact?
No. FuelEconomy.gov frames it as an average estimate. The real effect depends on tire type, vehicle weight, speed, road surface, and how far underinflated the tires are.
Will higher-than-placard pressure improve MPG even more?
Follow the vehicle manufacturer's recommendation on the doorjamb placard. Overinflation can affect handling, traction, and tire wear. For safety guidance, see NHTSA tire materials linked in the sources below.
Does tire pressure matter for EVs too?
Yes. Rolling resistance affects energy use regardless of fuel type. For EV cost math, see: EV charging cost per mile.
What if my MPG is still bad after fixing pressure?
Tire pressure is one lever. If MPG remains low, check other common causes and stack effects (driving style, idling, cargo drag, maintenance issues). Start here: why is my car getting bad gas mileage.