Actually here is some more tips from the same website. Some of them seem pretty good ideas. Some I question like buying your gas at night but still interesting read
Don't buy gas with greater octane rating than the auto manual recommends. Some think that higher octane ratings mean high quality gas but that isn't true. If your manual says to buy regular gas (usually 87 octane - it's stated on the pump), than you are wasting money paying for premium. Optimal performance is obtained when using gas with the octane rating the engine was designed for. Using mid-range or premium octane gas costs more and will not result in superior performance. However, older vehicles may require these grades to avoid "knock" which reduces power and may damage the engine.
Keep your tires inflated at the recommended tire pressure. This is very important yet somewhat counterintuitive. Under inflated tires will get poorer gas mileage and shorten tire life. Keep a close eye on your tire pressure. Check your manual for proper inflation pressures.
De-Junk the trunk. An extra 100 pounds can degrade fuel economy by 2 percent. That means if the price of gas is $3 per gallon, with that 100 pounds of junk you are paying $3.06 per gallon. It adds up.
Use a light foot. Gently accelerate. Acceleration is where most gas is consumed. It takes relatively little gas to maintain a constant speed.
Also drive slower, higher speeds consume disproportionately more gas (easier said than done). One study reported that for all vehicles tested there was at least 20% loss in fuel economy as cruising speed was increased from 55 to 75 mph. So, 20 mpg at 55 mph becomes 16 mpg or less at 75 mph.
If you have an instant MPG (miles per gallon) meter, use it to gage yourself.
Also use cruise control on highway trips.
Stop your engine if idle for 30 seconds or longer if it's safe to do so.
Don't fall for those gas-saving gadgets, oil treatments, etc. Consumer Reports have tested the dozens of so-called gas-saving engine accessories and found that they deliver nothing but hot air.
Ditch the roof rack unless absolutely necessary. Even an empty one will catch the wind and cost you mileage.
Reduce the use of your air conditioner at low driving speeds. However, when driving over 40 mph using the air conditioner costs less fuel than having windows open.
Park in the shade and/or leave windows slightly open to reduce the need for air conditioning.
Do not overfill the tank. After the auto-fill nozzle clicks off, don't allow service station personnel to "top-off" the tank if they are using the vapor recovery nozzles. These recover more than just gasoline vapor for the station.
Calculate gasoline mileage periodically. Declining mileage can be an early indicator of mechanical problems or a need for servicing.
Purchase your gasoline when it's coolest outside such as in the early morning or at night. Gas becomes denser in cooler temperatures. Since gas pumps only measure the volume of fuel - and not the density - you'll get more gas for the money and therefore greater overall gas mileage by purchasing fuel when it's cool outside rather than in the heat of the day.
Don't drive with open windows when traveling at high speeds. Open windows on the highway can reduce fuel efficiency by 10%. It's much better to use the ventilation system.
Stretching Your Gas Dollars