Pensioner surmised:
"if the overall gearing is the same (tire size,&final drive and top gear
ratio )'
the revs/mile or rpm/mph will be virtually identical."

Since I'm not a gear ratio/rpm expert, I will leave this to you experts.



Am I turning lower revs to get the same speed a WBX does?

I have two WBX Vanagon Westfalias in my driveway that have same size tires,
and are lighter. My I-4 Westfalia has same size and type tires, weighs more
than the other two Westfalias:
Extra propane tank, two catalytic heaters, roof rack, Behr air conditioner,
fog lights, trailer hitch, for mudflaps, auxiliary deep cycle battery, smart
charger, solar panel, cd changer, power amp, and subwoofer. No wonder it's
sits lower than the others!( -I hope it's all still there in the morning)!

Both other Westfalias are bare stock.
The route traveled, weather, fuel, distance, the same.
I suppose I should use the stop watch between mile posts.

Non of what I claim may be convincing-a ride in all three on the same route
might be-The WBX are all in top running condition.

This is a feel test. A see test.  take it for a ride and you will feel the
difference. You will see the difference, as you can easily merge into traffic
up 75 mph in third. merging on to freeways here in America's 2nd worst
traffic is a challenge for the WBX westies. I almost always have to slow down
to 50 to get behind the traffic in the right lane, which is no safer, as then
drivers approach your rear at 70 and change lanes to pass you at the last
minute.

I am not a scientist, I don't have a wind tunnel, or a Bunsen burner (will a
one burner Coleman do)?
But, if you can ever make it out this way,
I can burn some Bunsen's if you will like to go for a test drive.

Regards from Seattle,

Robert