Rev to at least 3000rpm in each gear and 3500 in 1st since the gap to second is so high. This way you're not going to far into boost and also avaoiding the 'nothing' zone below 2500 rpm.

My '03 Wagon gets 26-27 mpg at 75 mph on the freeway with wife, kids and gear.

 

I agree with the 3k rpm being the most economical.
The problem is it's hard to always drive like that.
I end up revving it high every now and then.

I used to average 280 before I had the catless
uppipe (Vishnu), catless downpipe(Gosspeed) and
a prodrive muffler. Now I average 320 miles.

 

The answer to this question is simple and it is basically the same for every car.

It's *not* to shift at the lowest RPM without lugging though.

The basic formula is this:

Find out what RPM your peak torque is at and which peak hp is at.

For best fuel economy, shift slightly above the RPM for peak torque so that you wind up at the peak torque RPM in the next gear.

For maximum acceleration, shift slightly about the RPM for peak hp so that you wind up at the peak hp RPM or slightly above in the next gear.

That is all you need to know.

 

BTW, as a confirmation of this, you'll notice that nearly every car is geared so that the RPM is very close to the peak torque RPM when you are driving at approx 60 mph in 5th gear (6th where applicable)

That is the point at which the car is moving itself along most efficiently.