Are you really so confused?
We have a 2004 Quest and 18.3mpg is a good average for us. It is most of the time city driving but even with having long trips I hardly ever reach 20mpg.
Last year we drove to South Carolina and we've finally seen 23mpg! This was the highest ever!!
And to make sure - I am not cruising around like crazy, because gas mileage is important for me, almost like a sport!

I have an 05 Quest 3.5S which I drive very carefully and an 18.3 mpg average would be good. Most of my driving is in town and my avg is about 16 mpg - in the summer using AC most of the time it's more like 15. On long highway trips driving 70-75 mph I get about 21 mpg (if I'm lucky). All my numbers are based on dividing miles driven by actual amount of gas I put in.

Drove another 07 Quest over the weekend and got 24.6mpg...based on approx 70% highway, 30% city.

SoccerDad, thought more about what you said and talked to the powertrain group. What you're proposing would probably help fuel economy a little, but the lower torque at the bottom and middle would mean that it would take forever to get to highway speeds.

Of course it's completely up to you (it's your van), but I'd say that the several hundred thousand dollars of man-hours that Nissan spent to tune the power is probably a pretty good place to be.

I'd like us to be exact about how we are measuring the fuel consumption and then we can really compare. The computer on my 07SE says that we get about 21 or 22 mpg on hwy and about 18 or 19 around town. I will measure it based on miles traveled / gallons used and report back. One thing I've thought about for improving performance (and fuel economy) is deleting the huge muffler that is in the middle of the exhaust. I was shocked when I looked under my quest to see about 20 mufflers and/or cats under there. (OK a slight exaggeration). I was thinking of bypassing and removing the largest one in the middle, which should give the exhaust a straighter shot, and relieve some weight. I don't deny this seems a little crazy, but I'd like to see what it does.

Due to the way we fuel and track the fleet vehicles, I'm not able to calculate fuel economy the way you're proposing, I can only go by the trip computer. It uses the electrical pulse of the injectors to measure fuel used, which is probably more accurate than assuming every fuel pump shuts off at the exact same top-off amount.

As for removing the muffler, I don't think I can even justify that with a response. You bought the car, you can do to it what you will.

I did say one of the mufflers, How many does the van need? I see two mufflers under there other than the large one that I would consider removing. The van is perfectly silent. Maybe I would trade improved flow for a bit of noise. It is not a permanent change, so what the heck, I might give it a try. Any other comments / suggestions?