Summarize this article in one sentence.
This part is just science: a lighter car uses less gas. What can make your car lighter? Not having a full tank. So when you hit that 1/3 of a tank and are tempted to fill up, give it a couple days. That last 1/3 of a tank may last you a bit longer than the first third did. That being said, it's generally true that gas prices spike up on the weekends, starting on Thursday afternoons. So if you think you'll need gas on Saturday, it might be wise to fill up now. Scope out any especially good gas prices to see if it's worth buying now. If you idle your car for more than a minute, it will save gas to turn off the engine. Also, new cars do not need to be "warmed up" on a cold winter day – a couple of seconds should do the trick. Whenever you're waiting for someone, turn off the idle. Drive thru or going inside? Going inside. You can still play the radio without idling! [citation needed] The gas nozzle is just connected to a regular hose. When you turn the hose off, there's still all that gas in the line. To get that last 1/2 cup of gas (that's 4 ounces of free gas!), turn the nozzle upside-down and give it a shake before you take it out of your tank. Lift up the hose a bit to get the gas resting in the line. Gravity causes the gas to lie at the lowest point, so lifting it up gets it out of there and into your tank. The better cooling method at freeway speeds depends on your car. Rolling down the windows creates drag, and using the air conditioning causes your engine to work harder. However, rolling down the windows is okay in city traffic. More science! The cooler your car is, the less gas will evaporate from your tank. That's like giving money to the sky. And did we mention that your bum doesn't get seared on contact? It's better for your car and for you. It's hard to drive when you can't touch the steering wheel without burning yourself! Fuel economy is worse in busy, high-traffic times or when it is raining, windy or when barometric pressure is high. Rain, headwind and high barometric pressure create extra air drag that uses more fuel to create and maintain forward motion.  However, a tailwind (a wind behind you) helps. Which direction is the wind coming from? It should come as no surprise that high-traffic times are not good for fuel efficiency. You're stopping and starting, idling, weaving, and probably taking part in just about every bad habit for your fuel economy. Sure, when we cut the engine, everything goes off, but what about when we start it back up? If you turn everything off, the next time you start up your car, it'll take way less gas to get everything going.[citation needed] You can then turn everything on one at a time, which is much easier for your car to handle. Try to consolidate errands and appointments. Get all your errands done in one go to increase your free time, too. You can also plan your trip on certain days to avoid traffic and paying higher gas prices the next week. For example, buy non-perishable necessities (including pet food, toilet needs, dry goods, and canned groceries, etc.) in bulk so you don't have to make a special trip for a few items.

Summary:
Drive until your tank is close to empty. Avoid excessive idling. Turn the gas nozzle upside-down when you're done filling up. Avoid rolling down your windows at high speeds, or using the air conditioning at all. Park in the shade. Try to avoid traffic and bad weather. Turn all electronics and climate control off before you cut the engine. Reduce the number of times you have to drive by thinking ahead.