To Air-Con or Not To Air-Con - Some Fuel Saving Tips To save you money
Fuel Saving Tips To save you money
So should you keep your car windows open in hot weather or should you close them and put on the air-conditioning?
Many drivers who hit the motorways generally close their windows as they speed up and turn on the air-conditioning.
Traditional wisdom would have it that you should close your windows and switch the air-con on at higher speeds, because the extra drag on the car can increase your fuel consumption and therefore higher fuel costs, specifically associated with keeping the windows open.
Putting the air-conditioning on at motorway speeds increases fuel consumption by about 3 to 4%, and can be up to as much as 10% in stop and start traffic.
Contrary to popular perception, that is wrong, according to the RAC. While the motoring organisation admits that many drivers will roll their windows up and start using their air-con when they reach above 30mph, it says that having your windows down and the air-con off is always better for your fuel economy - whatever your speed.
A study by General Motors and engineering standards organisation SAE compared fuel use in a saloon and SUV at speeds of 31mph, 50mph and 68mph, And it found that - in both cars at all speeds - having the windows open was more efficient.
The Society of Automotive Engineers (SAE), is a U.S.-based but globally active professional association and standards developing organisation for engineering professionals in various industries. Principal emphasis is placed on transport industries such as automotive, aerospace, and commercial vehicles.
Most people who are sweltering in their cars would probably prefer to have the windows rolled down but feel that the drag will cost them money in fuel consumption, so it's worth remembering that having windows rolled down is definitely the cheaper option, if not always the cooler one. It’s also worth remembering that air-con will stop working if not used regularly, so you should switch it on every now and then.)
Here is another fuel and money-saving tips while driving: Don't fill up your fuel tank to the very top. The RAC says that 99% of people do this - but it's not the best way to fill up. You should fill your car until the nozzle clicks, and stop there.
If you fill the tank right up to the brim, then you leave no room for fuel vapour to expand inside the tank, and can damage your car’s vapour collection system. The RAC says: "Replacement isn’t cheap, and inefficient fuel vapour collection is also bad news for the environment." 
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Justin Kavanagh
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