Time to switch on your car’s air conditioner on level 4 and let the ice-cold gale-force wind blow past your face. Or is it more efficient to just roll down your windows?
This is a popular myth, thanks to an episode of the TV series MythBusters. The show put two SUVs to the test – one with windows closed, and AC off, and the other with no air conditioning and windows open. Both vehicles were given the same amount of fuel (five gallons) and driven around a track until they hit empty at 45mph. In the end, the SUV with open windows outlasted its air-conditioned companion, getting an extra 15 per cent in mileage.
As speed increases (such as on a highway), so does wind drag, causing the engine to work harder to maintain progress, making AC more efficient.
Because the original tests during the TV episode were inconclusive (a second test at higher speed used a computer to estimate fuel efficiency based on air intake, not actual fuel consumption, and showed A/C was more efficient), this myth was revisited in a later episode in which it found that air conditioning is more fuel-efficient when the car is travelling approximately 50 mph or more.
If you do not use your AC regularly, then the coolant in the system will not circulate around and the lubrication will not be able to work as it should
Should you start your engine with the AC on? This bit of advice applies to older cars. Engines that have just been started are not very efficient and, on older carburetor models, the AC compressor can present a huge power load on start-up. It is thought that doing this over time would shorten the life of an engine. In modern-day cars, accessories are mostly automatically shut down during the starting procedure.
Your AC can help you out all year long, not just when it is hot in the summer. Those mornings that you get in your car and your windscreen is all fogged up can be easily sorted out with a quick blast of your AC. If you do not use your AC regularly, then the coolant in the system will not circulate around and the lubrication will not be able to work as it should.
Turning it on also gets rid of any moisture build-up. If these build-ups are left, then they will become a breeding ground for mould and bacteria to grow.