Yes, hot weather can reduce gas mileage in most vehicles, but the drop is usually modest. The biggest reasons are extra air conditioning use, more idling in traffic, and hotter road conditions that raise rolling resistance.
Here's what you need to know:
| Cause | Effect on gas mileage |
|---|---|
| Air conditioning | Uses extra engine power, especially at low speeds |
| Hot pavement | Can slightly raise tire drag |
| Low tire pressure | Reduces MPG and gets worse in heat swings |
| Stop-and-go summer driving | Burns more fuel than steady highway driving |
According to the U.S. Department of Energy, air conditioning can lower fuel economy, especially in city driving where the engine works harder at lower speeds. AAA also notes that driving with low tire pressure can cut fuel economy and raise wear, which matters even more when temperatures change fast.
Hot weather alone does not always cause a big MPG drop. In steady highway driving, many vehicles lose little or no mileage if the driver keeps the A/C use moderate. In city traffic, the drop can be more noticeable because the compressor, cooling fans, and frequent stops all add up.
Extreme heat can also make a car work harder in other ways. The cooling system may run more often, oil can thin faster, and hot tires can change pressure. If your tires are underinflated, fuel use goes up. The U.S. Department of Energy says proper tire inflation can improve gas mileage by about 0.6% on average, and up to 3% in some cases.
If you want better summer MPG, use these steps:
- Keep tires inflated to the door-jamb sticker pressure.
- Use recirculate mode with the A/C when possible.
- Park in shade to keep the cabin cooler.
- Drive smoothly and avoid hard acceleration.
- Remove heavy items from the trunk.
- Check the engine air filter and cooling system if MPG drops a lot.
A useful rule: if your mileage falls only a little in summer, heat is probably the reason. If it drops a lot, look for tire pressure problems, A/C issues, or a maintenance problem.
Sidekick can help you track fuel costs over time, spot MPG changes, and estimate how much summer driving is costing you each month.