Sorry to be a pain, but I have to dispel this myth.
Yes when you have higher rpms theres more air flowing through the carburetor pulling in more fuel... but that is on an engine with a carb and our fuel injected engines do not have that.
There is no relation to rpm and fuel that is injected, fuel is NOT injected for every turn of the crankshaft it is pulse width modulated, meaning fuel is injected the same number of times every second regardless of anything you do, what changes isnt how often it's injected but how long it holds the injector open (pulse width). Engine rotation is not a factor of fuel economy, it is only load and throttle input. load could possibly be increased a minuscule amount at higher rpms, but this is not a big factor, what IS a big factor is efficiency. (now someone correct me if on the new direct injected explorers this isn't the case, but I find this highly unlikely, but if so then everything im saying may be incorrect)
The way you can tell how efficient what gear youre in is, is by how much throttle you give it. Now you may be able to put it in sixth at say 30 mph, but if you need to give it half throttle to make it go that fast you are using WAY more fuel then if you dropped down a few gears and only gave it say a quarter or eighth throttle.
As always pay attention to how far down your right foot is to tell how much gas you're using.
Kiliona you misread my post regarding carburettors. You misquoted me in your response, please reread to see what I actually said.
Hope I can fill some gaps in your understanding, then you might be better prepared to dispel, instead of create, some myths, since that is what you are apparently aspiring to do in your posts.
Fuel is NOT “injected the same number of times every second regardless of anything you do”, as you wrote. While very imaginative, it's incongruent with the science of the workings of a Direct Injection engine.
The fuel is injected when the computer commands it to, which, depending on load and throttle position, and hundreds or thousands of other parameters, can be at various points during the compression, or intake strokes. It is also capable of delivering multiple pulses of fuel during an individual stroke. The control is extremely tight, measured in milliseconds. This will as a result directly vary the rpm to suit the conditions called for.
Not only is the pulse width of the fuel modulated, and its timing during the cycle, but the fuel pressure is tightly controlled as well, by more than an order of magnitude.
You also wrote “Engine rotation is not a factor of fuel economy, it is only load and throttle input”.
Once you are up to your cruising speed, if you are not in top gear (as I pointed out, the transmission will not allow you to lug the engine) then your engine is rotating more turns per mile than it needs to, as measured not only in revolutions per MINUTE on your tach, but more importantly to fuel mileage, revolutions per MILE. The drive ratios are carefully chosen to optimise fuel mileage. That is one of the main purposes of the top gearing in the transmission, to allow the engine to make fewer rotations per distance travelled and burn less fuel, if it were not so, why would they exist?
Also note that, under normal conditions, if you shift into a higher gear, and want to maintain the same speed, (if any throttle change is needed at all) it will require that you decrease your throttle, not increase it. If you maintained the same rpm and accelerator pressure, with an upshift you are now in a higher gear with the engine turning over fewer times to make the drive wheels turn at the same speed. Slightly lifting your foot from the accelerator at the right time can in fact cause an upshift, with no increase in speed. Most drivers do this subconsciously without even thinking about it, it's so seamless.
