I've always wondered if you could get better millage with airless tires. I haven't bothered to investigate because I think they are too far off in the future to be practical. Just wonder sometimes.
I'm happy my 2010 Prius is on 15" tires, cheaper (as noted) and the ride is still decent even at high pressures. Now that warm weather is here, we are getting a steady 47-50 indicated (hand calculates to about 5% less). We are perfectly happy with this. My wife (it's primarily her car as I work from home) says she's a hybrid girl for life and hopes to drive the wheels off this one.
Seems like a number of these questions and statistics could be answered if we all used fuelly.com I live my Fuelly stats
Apples and oranges. Almost everyone here tracks their average MPG, but tracking what you are getting now, doesn't let you figure/project what getting a totally different average MPG would cost you.
Even though I had to take multiple years of math in college, I still like to keep things simple. A gasoline engine will last over 300,000 miles without much effort. That's the typical lifespan. So: 300,000 miles/40mpg == 7500 gallons 300,000 miles/50mpg == 6000 gallons 300,000 miles/60mpg == 5000 gallons (hypermiling prius) Difference between 40 and 50mpg is 7500-6000 gallons * $3.50 per gallon == $5,250 over the life of the car. Hypermiling to raise your 40mpg average to 60mpg will save you $8,750 in fuel costs.
We are used to thinking in miles per gallon (mpg), but when considering cost it is easier to flip the fraction over and think of gal. per 100 or 1000 miles. A Prius that gets 50 mpg uses 2 gal. every 100 miles and 20 every 1000. Another car that gets 40 mpg uses 2.5 gal. per 100 miles and 25 per 1000. At $4 per gal., the Prius savings is $2 per 100 miles and $20 per 1000.
With these numbers, I am getting around 45-46mpg with my 17" wheels. Though this is not totally due to the as I live in a hilly area. So cost wise the difference between 45 and 50(assuming that's what I can hit with 15" wheels), is $133 annually for gas. $11 per month.
Try this: If you drive 15,000 miles per year how many gallons do you use at 25, 50 and 100 mpg? 25 mpg: 15000/25 = 600 gal 50 mpg: 15000/50 = 300 gal 100 mpg: 15000/100 = 150 gal So you see going from 25 to 50 mpg saves you twice as much gas as going from 50 to 100 mpg. And you can never save as much as going from 25 to 50 unless you go to zero gas. Mike