But I want my full size SUV and 30mpg
Seriously though, I firmly believe we can do much better in terms of MPG. The technology is right in front of us.
I've been happy with my 07 thus far. It consistently gets 21mpg on the highway (long trips) and averages around 19 on the daily route to work with the AFM 5.3. I'm sure that an intake, full exhaust, and a tune would bump that up another 1-2mpg. While the ~$1300 investment only saves about 2 cents per mile (takes ~70-80k miles to get a positive return on the investment versus fuel cost), it still saves some money in the long run since I keep my personal vehicles to at least 200k miles.
With that being said, if the OEMs (and this country in general) would accept diesel engines, I'm confident that my 07 with something like a small 3.0L turbo diesel would knock down 25-26mpg right off the factory floor with all the smog and noise equipment. A few mods added afterwards would surely increase that to 28mpg or better. Again, not a lot of gain, but I can still drive a lot further on a single tank of fuel... and if you keep a small fuel storage at home like I do (~20 gallons), it's good insurance against short term fuel shortages and price spikes since you can drive more miles on any given amount of fuel.
The savings is even greater for businesses.
Take two of my fleet trucks into consideration for a minute. Both are 05 2500HD crew cab 4x4s. One is the 6.0 vortec and the other a duramax. The 6.0 is lucky to get 16mpg on the highway on a good day, while the duramax, despite being a larger engine and makes a lot more power, will knock down 19-20mpg easy. Visit some duramax truck forums and it isn't unusual for lightly modded duramax trucks to get 21-22mpg.
For a company like mine, which spends ~$10,000 per month on gas currently, just a couple of mpg difference saves a lot of money.
While this deviates from the original discussion on AC and MPG, the savings is something to consider.
