Originally Posted By: Titan
Right...but, it's also warmer. So, which had the most effect on the fuel economy? There is a point where harder tires actually increase rolling resistance...as they tend to skitter more across the road surface, which increases friction. It depends upon the contact patch, the suspension's abilities to eliminate the skittering, and the roughness of the road.
Also, I think it's interesting that the biggest changes in mpg are right next to one another. This shows that more complete or less complete filling of the tank is probably the cause. Overall, the TREND is what is important, and, the lowest mpg come in the coldest months...which is to be expected.
Not true at all. My tires are rated for 34 PSI, but I pumped them up to 50PSI, and my MPG increased 12% just doing that alone. Grip, performance, turning, and braking are nearly the same as if the tires were set to the recommended PSI. Tire grip and wear are excellent, no worries. More PSI means less tire patch on the road, but not so little to cause any safety worries. More PSI means lower rolling resistence. Most tires can safely handle 100 PSI, as this durability was engineered into them to cut down on losses from lawsuits. I'm about 3/4's through my tire's thread and so at 35,000 miles, I should be able to get to 45,000 or 50,000 easily before needing to change them.