In a no-wind situation... you are essentially trading time for fuel..
your max range versus power settings wont have a very significant
difference.. say.. 10% from the high value to the low value(this is
based on my experience in normally aspirated piston single engine 4 seat
aircraft)

Even turbocharged, the equation still applies.. time for fuel.. I can
make a big dash up high to say.. 25K feet.. and up there 200 INDICATED
gives me 300 TRUE on a standard day.. but you still have to burn pretty
much the same amount of fuel to maintain that "indicated" airspeed
(again.. 5-10% fudge factor).

So.. In the Velocity my friend is building, that we are gonna turbo.. we
can make a high power climb up high to that hypothetical 25,000 ft.. and
maintain that 200 mph indicated for 300 true.. but we will go through
our 60 gallons of fuel in a little under 4 hours.. and go about 950 SM..

We can fly lower/slower at a lower fuel burn and power setting.. and go
the same 900 or so miles, but take 5-6 hours to get there.

One benefit someone else mentioned is.. get up higher and get a
favorable tailwind.. and that will pay you sweet dividends on your time
and groundspeed.

Dave

(by the way.. if someone tries to replicate my fuel burn numbers.. this
was hypothetical.. I found an error in the power calcs we were making at
altitude.. and I think the fuel burn is actually low.. have to revisit
it.. I KNOW they have an error.. I used em to illustrate the concept)

Ben Jackson wrote:
For a non-turbocharged piston airplane, does cruise altitude really
matter? I made a complicated spreadsheet which produces a fairly simple
answer: Unless you climb way above your critical altitude, trip time
and fuel burn don't vary much at all. Over a 500nm trip, it only takes
about 4% longer to fly at 3000MSL instead of 7000 (approximately critical
altitude) and 7% longer if you go clear up to 13000. For my plane that's
a difference of about 7-15 minutes out of 3+ hours.

How high does your critical altitude have to be (due to turbocharging
or jet/turbine) before it really starts to matter what your cruising
altitude is?