HONOLULU (KHON2) — Did you know hot weather can actually increase your fuel economy? Your engine warms up to an efficient temperature faster, summer grades of gas can have slightly more energy than during the winter and warm air causes less aerodynamic drag than cold air.

That’s according to the Environmental Protection Agency (EPA). And while Hawaii typically has the ideal temperature for this, there are also some summertime behaviors that can reduce your fuel economy drastically. Here’s what to avoid.

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Avoid running your car’s AC when the weather is hot. Under very hot conditions, it can reduce a conventional vehicle’s fuel economy by more than 25% on short trips. This number may be even larger on hybrids, plug-in hybrids and electric vehicles. The EPA says pre-cooling the cabin while plugged into a charger can extend your vehicle’s range, and using a warmer temperature setting for the AC will use less battery power.

For both gas and electric cars, the EPA advises drivers to not use the AC more than needed or to set the temperature lower than needed. Running the AC is a main contributor to reduced fuel economy in hot weather, so don’t idle with the AC running before driving. Plus, most AC systems will cool the vehicle faster while driving.

The EPA also says driving with your windows down can reduce your fuel economy since open windows can increase aerodynamic drag (wind resistance), which makes your vehicle use more energy to push through the air. It’s not as bad at low speeds but increases on highways and freeways.

So, if you need to cool down during the hot summer months, roll the windows down at lower speeds, and use the AC at highway speeds. Drive with the windows open for a short time before using the AC, so you let out the hot air first, putting less demand on your AC. This will help cool your vehicle faster.

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The EPA says most manuals will explain how the AC system controls work and how to best use it.