Help me understand the basic theories of fuel consumption!

[Ginsu]

So I was looking at this chart on the Nissan website: http://www.nissan.ca/vehicles/en/ and I thought to myself, "Yeah, everything is in the right place. Heavy Titan and Armada on the right, light Versa and Sentra on the left." But then I thought what about when the issue is not simply weight but power and performance? The Altima, Maxima, 350Z, and GT-R are all V6 engines and roughly the same weight (relatively speaking at least) but there's a clear progression between these cars' fuel consumption. So I ask you guys, why is each in this list of four more thirsty than the last?

I know, I know, more fuel injected = more fuel burned, and performance cars with a turbo influencing the fuel monitoring system love to push tons of air and fuel into the combustion chamber, BUT, why doesn't the faster burn rate increase the power output and in turn reduce the amount of fuel required to achieve a set speed. For example, if all four cars were in a line and they drove down the same road and set their cruise at 50 mph, why wouldn't the extra fuel injected into the GT-R cause a corresponding increase in power output which would then trigger the cruise control to ease up on the throttle a little bit and reduce the fuel input? The maintained rate of consumption would then more or less match the other cars, would it not?

I know there's got to be a problem somewhere in this circular logic, but I don't know what it is.

[blindsnyper]

you are a few things:-gearing: higher rpms=more fuel being used. lower rpms=less fuel being used, UNLESS under a load.-wind resistance/aerodynamics: pretty self explanitory-and just how easily the vehicle rolls in general: umm....yeah

i may be completely wrong on all this, but it is how i look at it

[mightyversa]

One thing that I have learned, and it boggles the minds of scientists today is Volumetric Efficiency. When I did the Auto Service Tech course in college, this was a topic that I loved to read about because once someone knows how to get the Volumetric Efficiency to 100%, he or she will become a billionaire!! Do some reasearch on it for if I start writing things down, it could take a page or 2.

In short, Volumetric Efficiency will help answer ALOT of our fuel consumption questions and why internal combustion engines strive to gain 100% efficient air to fuel ratio's that can result in better gas mileage!!

[Shad0wXCalibur]

Although the higher up cars have bigger engines, highway mileage should be pretty close. City will just suffer.