Use our online catalog... Use our dealer locator... Oregon DOT report offers perspective for all states EIA: Another big decline in oil inventory, gasoline production Russia says no oil production cuts OPEC agreement to cut production? Don't bet on it. Car manufacturers push for quieter tires The end all verdict to A/C vs. windows down! Posted in: Car Maintenance, by Patrick DeHaan on Jul 22, 2011 12:41 PM There have long been battles between people investigating A/C vs. use of windows, so let's face it, will we ever find a true solution that always holds true? Perhaps not, but we may get close.For the ultimate verdict I was going to compare several credible sources and ultimately see if there was any sort of rhyme or reason to their research and testing, if they did any.. While definitely not a leading researcher, they've looked at published reports from credible sources and seemingly have a good fix on this battle. , "Based on a study conducted by the Society of Automotive Engineers (SAE), driving with the windows up and the air conditioning on is typically a more fuel-efficient way to drive [source: Hill].

We'll get around to discussing when air conditioning isn't a more efficient option, but let's first take a look at what the SAE found.The SAE study was conducted at a General Motors wind tunnel and on a desert track. In the wind tunnel, air was forced over the front of the car and also from an angle on the front of the car to simulate a cross wind. In the desert, temperatures and vehicle speed were factored into the study. Two vehicles were used in the test, one was a full size SUV with an 8.1-liter V-8 engine and the other was a full-size sedan equipped with a 4.6-liter V-8 engine. Overall, both studies showed that driving with the windows down has a significant negative effect on the fuel efficiency -- more than using the vehicle's air conditioner.For the sedan, when the windows were down, the efficiency was reduced by 20 percent, while the SUV fuel efficiency was reduced just 8 percent [source: Hill]. These differences are an important factor in determining just how much the windows down option will affect the fuel efficiency of your vehicle.

The study concluded that the more aerodynamic the vehicle, the more drag open windows will create.When driving at speeds of more than 55 miles per hour (88.5 kilometers per hour) with the windows down, there's a decrease in fuel efficiency of 20 percent or more. best value ac unitAlthough using the air conditioner decreases fuel efficiency as well, cooling the air through the compressor only decreases the fuel efficiency by about 10 percent [source: Arthur].sizing ac unit to houseSo, when traveling at speeds around 50 miles per hour (80.5 kilometers per hour) or faster, air conditioning is usually a better bet, but what about when you're simply cruising around town? new ac unit installed costKeep reading to find out how you can save a little bit of fuel on those slow-speed short trips."

So HSW says that for faster speeds, A/C is better. Now on to the Chicago Tribune, another credible source:"The higher the speed, the more wind resistance affects mileage. So, you may be saving gas by driving with the windows open and the AC off at 25 mph. But at 55 mph and faster your vehicle's aerodynamics are increasingly degraded by open windows.At highway speeds you may get better mileage with the windows up, but it may still not be better than it would be with the AC off."Poking around city traffic, aerodynamics doesn't come into the picture very much," said auto air-conditioning guru Ward Atkinson. The auto engineering consultant worked on some of General Motors' first auto AC systems in the mid-1950s. He's a regular speaker on climate control at Society of Automotive Engineers confabs.While wind resistance from running at highway speeds with your windows down may eat up more gas than running windows-up with the AC on, there is no escaping the fact that "it takes energy to cool a car," Atkinson said."

So the ultimate answer- WHEN is best to use A/C over windows and vice versa? If you're driving under 45mph or so, using your windows is better. If driving faster than 45mph or so, using the A/C to keep cool is better.So, the verdict does appear unanimous! Use that A/C on faster roads or highways, but not while in the city or traffic. Keep your cool with our Air Con Servicing. Halfords Car Air Conditioning Services Did you know your air conditioning loses charge every year, making it less efficient and making your car warmer? Our air conditioning services keep your air con working properly by checking and topping up the refrigerant levels. This also involves cleansing the air circulation system to maintain icy cold air output and get rid of any nasty odours - and the harmful bacteria that cause them. Main car dealers can charge the earth for this service, but at Halfords we can do it for you for a competitive price - meaning you can keep your cool and get rid of that wet-dog smell for less!

Our in-store professionals can offer you the following services: We now offer a FREE air con check, to check your refrigerant levels and see if they need to be topped up for optimal performance. If they do need topping up, you can purchase all of the air con essentials from store to recharge at home or, you can book in for our air con recharge service and we can take care of it for you. Our trained in-store specialists can check your air conditioning levels and top up the refrigerant for you for only £30 (€35) as part of our air con recharge service. Pre-booking may be required, so be sure to contact your local store to check first. Air Con Recharge is subject to vehicle inspection. Air Con Recharge and Clean Service For the ultimate air con service, our experts can recharge your air con and clean the system at the same time for only £40 (€45). Included within the recharge and clean service is the air con cleaner product. Please note that some pre-booking may be required and all services are subject to vehicle inspection - just ask in your local store for more details.