NEW YORK – An Edmunds.com test found that some of the gas-saving advice drivers commonly hear doesn’t make much of a difference.Drivers tested the 2005 Ford Mustang GT and the Land Rover LR3 SE on the same 56-mile route eight times under various driving conditions for the study.The Mustang gets 15 miles per gallon (mpg) in the city and 25 on the highway under its EPA-estimated mileage, while the Land Rover gets 14 mpg and 18 mpg respectively, according to Edmunds.Many drivers use cruise control to prevent "speed creep" – the tendency to gradually accelerate – and save gas. The Land Rover was tested at 14 percent better mileage using cruise control set at 70 mph rather than maintaining a speed range of 65-75 mph. The Mustang was a better by 4.5 percent.Some believe that driving with the windows up and the air conditioning on prevents and aerodynamic drag, while others say that the AC uses too much fuel.Driving at 65 mph, The Mustang had 4.1 percent better gas mileage with the windows down. The Land Rover saw an improvement of just 1.6 percent, or 0.3 mpg. The Edmunds report said that either method works because the difference is so insignificant.Drivers should be warned to avoid hard acceleration. The test showed that slowing zero-to-60 times to 20 seconds rather than 10 or 15 seconds saw increased gas mileage of 35.4 percent for the Land Rover and 27.1 percent for the Mustang.If tires are not properly inflated, it can also cause a small decrease in gas mileage, but Edmunds recommends keeping tires inflated for general safety anyway.